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Earthquake Environmental Effects (EEEs) such as surface faulting, landslides, liquefaction and tsunamis are widely distributed following strong seismic events and may account for a significant part of the overall damage. Here, we investigate EEEs generated by two earthquakes with different source parameters, both occurring along the Mexican subduction zone: the Sept. 8, 2017, Mw 8.2, moderate depth, normal fault, intraslab event; and the June 23, 2020, Mw 7.0, shallow depth, thrust fault, interface event. We document all the EEEs for each event, assign an intensity value using the Environmental Seismic Intensity (ESI-2007) scale, and derive the macroseismic fields. Finally, we compute the attenuation of intensity with distance and we compare it with other subduction zone earthquakes worldwide, demonstrating the repeatability of EEEs. This work represents the first application of the ESI-2007 scale to an intraslab earthquake and documents its wide applicability in different seismotectonic settings. We argue that EEEs provide useful information that should not be neglected in seismic hazard assessment procedures.

Durante il Permiano Inferiore, l’evoluzione post-Varisica dell’attuale regione Alpina è stata caratterizzata da una importante estensione crostale combinata con intensa attività magmatica, che ha favorito lo sviluppo di bacini estensionali intra-continentali con deposizione di sedimenti vulcanoclastici (e.g. Bacino Orobico). Nel settore centrale delle Alpi Meridionali, l’apertura di questi bacini era controllata da complessi sistemi di faglia, attivi contemporaneamente con l’intrusione di plutoni e l’attività vulcanica in superficie. Il seguente progetto di dottorato si focalizza sullo studio di queste caratteristiche, con l’intento di approfondire i processi geologici attivi durante il Permiano. Diverse faglie di età Permiana sono state indagate nel Bacino Orobico, con particolare enfasi sul riconoscimento dei loro tratti originali, poiché esse sono eccezionalmente sfuggite alla deformazione Alpina. Nel passato, l’architettura dei bacini Permiani era stata descritta con strutture a horst-graben, formatesi in risposta ad una tettonica transtensiva controllata da una zona di taglio che ha portato alla trasformazione da Pangea B a Pangea A. Tuttavia, studi più recenti hanno indicato un diverso setting di faglie che hanno controllato l’apertura dei bacini Permiani: si tratta di una combinazione di faglie normali a basso e alto angolo. Le faglie normali a basso angolo identificate lungo il Bacino Orobico rappresentano il miglior luogo in cui osservare l’interazione tra attività tettonica e magmatismo, poiché i loro nuclei di faglia sono caratterizzati da cataclasiti sigillate da livelli di tormaliniti. Queste ultime testimoniano la circolazione di fluidi arricchiti in boro e incanalati lungo importanti zone di faglia correlate all’apertura del Bacino Orobico. Simili brecce a tormalina affiorano anche in Val Trompia (BS): molti autori hanno suggerito che le tormaliniti delle Alpi Orobie, quelle della Val Trompia unitamente alla mineralizzazione di uranio del distretto di Novazza-Val Vedello potrebbero essere geneticamente correlate. Esse potrebbero essere correlate ad un sistema idrotermale di alta temperatura su ampia scala, coevo con l’attività tettono-magmatica del Permiano Inferiore che è responsabile anche della messa in posto di svariati depositi di minerali metalliferi nelle Alpi Meridionali. Tuttavia, la genesi delle tormaliniti non è mai stata dettagliatamente caratterizzata e la loro connessione con i giacimenti di U finora non è mai stata investigata. Le faglie tormalinizzate sono state riconosciute in molte località del settore centrale delle Alpi Meridionali quando ancora non era nota l’importanza delle faglie normali a basso angolo. In questa tesi di dottorato, vengono caratterizzate tutte le aree con i ritrovamenti di tormaliniti, ricercando la causa dell’idrotermalismo regionale nel contesto di estensione durante il Permiano Inferiore. Inoltre, per via del possibile link con i giacimenti di uranio, lo studio dei borosilicati viene proposto come strumento per meglio caratterizzare la genesi delle mineralizzazioni. Nuove osservazioni di terreno su tormaliniti sono combinate con lo studio della geochimica dei minerali e della roccia totale, insieme alla geocronologia, a studi microstrutturali e analisi isotopiche del B, con lo scopo finale di definire l’origine di questi fluidi arricchiti in boro. I risultati ottenuti da questa ricerca dimostrano che le tormaliniti e il magmatismo Permiano sono in stretta correlazione temporale e genetica. Inoltre, i dati geochimici sugli elementi in tracce forniscono maggiori indizi su una diretta connessione tra tormaliniti e la mineralizzazione a U dell’area di Novazza-Val Vedello. Tutti questi dati, per concludere, sono discussi nel contesto di interazione di processi tettonici, magmatici e di formazione di giacimenti che hanno interessato l’attuale settore centrale delle Alpi Meridionali durante il Permiano Inferiore. During the Early Permian, the post-Variscan evolution of the present-day Alpine region was characterized by crustal extension combined with strong magmatic activity at different crustal levels, which finally led to the development of intracontinental extensional basins filled with volcanoclastic sediments (e. g. the Orobic Basin, N Italy). In the central Southern Alps (cSA), the opening of these basins was controlled by complex fault system that were active at the same time of plutons intrusion and volcanic activity at the surface. Relationships among magmatism, tectonics and hydrothermal activity related to the formation of ore deposits in the Early Permian so far have been only briefly addressed. This Ph.D. research project focuses on the investigations of the above described features, trying to consider the geological processes active in the Early Permian in an integrated scenario. Several Early Permian faults of the Orobic Basin have been investigated with special emphasis on the recognition of their original features, as they have exceptionally escaped most of the Alpine deformation. In the past, the architecture of Permian basins was described as horst-and-graben structures, formed in response to wrench tectonics developed during the activity of a megashear zone that led to the Pangea B to Pangea A transformation after the collapse of the Variscan orogen. However, thanks recent studies, a different fault architecture has been suggested to had controlled the opening of the Permian basins: a combination of Low-Angle Normal faults and High-Angle Normal Faults. The identified LANFs of the Orobic Basin represent the best site to study the interplay among tectonics and magmatism, as they are characterized by cataclastic bands sealed with cm to dm thick layers of dark, aphanitic tourmalinites. These latter are proof of fluids circulation channelled along higher permeability fault zones related to opening of the Orobic Basin. Such tourmaline breccias also crop out in the Trompia Valley (BS): several authors suggested that tourmalinites from Orobic Alps, tourmalinites from Trompia Valley together with uranium mineralization of Novazza - Vedello Valley are genetically linked. They are seen as products of a large-scale high-temperature hydrothermal system coeval with the Early Permian plutonic-volcanic activity and tectonism, which was also responsible for the emplacement of various types of magmatic-hydrothermal ore deposits in the Southern Alps (Sn-W, U-Mo-Zn, Fe carbonates, sulphides, quartz). However, their genesis has never been fully characterized and the connection between tourmalinites and U ore bodies has also not been deeply investigated so far. The tourmalinized faults were first noted in various sites of the cSA during the 90’s, when the tectonic importance of LANFs was not yet recognized. In this thesis, all the occurrences of tourmalinites are characterized, looking for the cause of the regional hydrothermalism in the context of intracontinental extension during the Early Permian. Furthermore, due to the likely connection with U ore deposits, the borosilicate study is proposed as tool for better understanding the genesis of the mineralizations. New field based structural analysis are combined with mineral and whole-rock geochemistry, geochronology, microstructural studies and boron- isotopic analysis of tourmalinites from different sectors of the study area, in order to evaluate the origin of these fluids. Results coming out from this study demonstrate, together with B isotope ratios, a temporal and genetical relationship between tourmalinites and Early Permian magmatism in the cSA. Furthermore, the geochemical data on trace elements provide more clues on a direct connection between tourmalinites and the U-mineralization. All these results are finally discussed in the frame of the interplay between tectonic, magmatic and ore generation processes that interested the present day cSA area in the Early Permian

On May 29, 2017, the MW6.6 Poso earthquake occurred in Central Sulawesi, Indonesia, causing moderate damages. The mainshock rupture and primary aftershock cluster occurred in the active Palolo-Sausu tectonic zone, and some aftershocks also took place around the Tokararu fault. However, the rupture mechanism of this earthquake and its relation to regional tectonics are not clear. In this study, the rupture process of the Poso mainshock is estimated by finite-fault waveform inversion, which is constrained by teleseismic bodies and surface waves. The rupture propagates upward unilaterally in a southwest-dipping moderate-angle (∼34°) normal fault beneath Tokorondo Mountains, with a notable ∼15% initial moment release at the first 4s of the ∼12s rupture duration. The average and peak slip are 0.5 m and 1.5 m, respectively. The rupture velocity is relatively slow (less than 2.5 km/s), and the Coulomb stress changes due to the mainshock are obtained using the inverted coseismic slip.

El análisis morfotectónico del sector central del Promontorio Balear, entre las islas de Ibiza y Mallorca, mediante batimetría multihaz y perfiles sísmicos de muy alta resolución ha permitido diferenciar varios rasgos morfológicos relacionados con la tectónica a dos escalas. Los elementos de gran escala, de dirección NE-SO, son: i) el escarpe Émile Baudot; ii) el monte submarino Émile Baudot, y iii) la alineación de montes submarinos Ausiàs March y Ses Olives. Los elementos de pequeña escala son: i) dos elevaciones longitudinales (ENE-OSO); ii) escarpes rectilíneos (NO-SE a NE-SO); iii) depresiones tectónicas (NNE SSO a NE-SO); y iv) alineaciones rectilíneas de pockmarks (NO-SE a NNE-SSO). Los elementos de mayor tamaño responden a la configuración estructural neógeno-cuaternaria. El escarpe Émile Baudot limita el Promontorio Balear y la cuenca oceánica del Mediterráneo Occidental. La alineación de montes submarinos Ausiàs March y Ses Olives está generada por una fase extensional, y el monte submarino Émile Baudot forma parte de una alineación volcánica NO-SE asociada a la Zona de Fractura de Ibiza. Los elementos de pequeña escala están relacionados con estructuras tectónicas activas que deforman las unidades sedimentarias del Cuaternario y el fondo marino. Las elevaciones longitudinales están generadas por pliegues anticlinales, mientras que el resto de estructuras están asociadas a la actividad de fallas normales de buzamiento alto. A morphotectonic analysis has been carried out between the islands of Ibiza and Majorca in the central sector of the Balearic Promontory using multibeam bathymetry and very high-resolution seismic profiles. Several morphological features related to tectonics at two different scales have been differentiated. The large-scale features have a NE-SW direction, they are: i) the Émile Baudot Escarpment; ii) the Émile Baudot seamount, and iii) the Ausiàs March and Ses Olives seamounts alignment. The differentiated small-scale elements are i) two longitudinal elevations (ENE-WSW); ii) rectilinear scarps (NW-SE to NE-SW); iii) tectonic depressions limited by one or two scarps (NNE-SSW to NE-SW), and iv) rectilinear pockmarks alignments (NW-SE to NNE-SSW). The largest elements respond to the Neogene-Quaternary structural configuration. The Émile Baudot escarpment is the limit between the Balearic Promontory and the Western Mediterranean oceanic basin. The alignment of the Ausiàs March and Ses Olives seamounts respond to the last extensional phase, and the Émile Baudot seamount forms part of a NW-SE volcanic alignment that could be associated with the Ibiza Fracture Zone. The smaller elements are related to active tectonic structures that deform Quaternary sedimentary units and the seafloor. The longitudinal elevations correspond to anticlinal folds, while the rest of the structures are associated to the activity of near vertical normal faults.

espanolLa zona geotermica de Pathe, en el sector central de la Faja Volcanica Transmexicana, ha atraido la atencion de exploradores y cientificos desde finales del siglo XVIII. El ingeniero de minas aleman Joseph Burkart (1798-1870), contemporaneo de Alexander von Humboldt (1769-1859), elaboro en 1836 una descripcion geologica de campo por la cual esta zona geotermica puede considerarse la primera en Mexico en haber sido investigada bajo los paradigmas de la ciencia moderna. Ainicios del siglo XX la zona fue estudiada por el ingeniero Jose Guadalupe Aguilera Serrano (1857-1941), quien en 1907 describio lasrocas eruptivas ysusproductos de alteracion. Su interes eran los yacimientos de caolin de Yextho, situados a un km de las manifestaciones termales. A mediadosdel siglo XX la zona ya se prospectaba como fuente de energia geotermica, lo que culmino en la primera planta geotermoelectrica del continente americano, en operacion entre 1959 y 1972 con una capacidad instalada de 3.5 MW.Las manifestaciones termales dePathe se ubican en la interseccion de dos sistemas regionales de fallas normales, con rumbos N-S y E-W, y estan encajonadas en una unidad volcanica (toba y lava) de composicion basica a intermedia y edad Mioceno superior. Las alteraciones hidrotermales superficiales son conspicuas y su distribucion esta igualmente controlada por fallas pertenecientes a ambos sistemas. Asociada a las fallas N-S ocurre la asociacion de alteracion calcita-yeso, que involucra fluidos oxidados y alcalinos ricos en sulfato. Por otro lado, ligados a las fallas E-W ―mas tardias― se hallan los depositos de caolin, producto de una alteracion argilica avanzada, caracteristica de zonas de condensacion de vapor. Las condiciones del fluido indicadas por esta alteracion son un pH muy acido (2–3) y temperaturas cercanas a los 100 °C. Por su clara asociacion con las fallas, asi como por la ausencia de vulcanismo reciente (Cuaternario) cercano, Pathe se considera como un sistema geotermico convectivo controlado por fallas.La sucesion de eventos de alteracion sugiere que la actividad hidrotermal inicio antes del Plioceno. EnglishThe Pathegeothermal zone, in the central portion of the Trans-Mexican Volcanic Belt, attracted a variety of scientists and explorers since late 18thcentury. Joseph Burkart (1798-1870), a German mining engineer and a contemporary of Alexander von Humboldt (1769-1859), provided in 1836 a geological description of the zone because of which Pathe was the first geothermal system to be studied in Mexico under modern science principles. At the beginning of the 20thcentury, this zone was investigated by the Mexican geologist Jose Guadalupe Aguilera Serrano (1857-1941), who described in 1907 the local volcanic rocks and their alteration. His main interest were the kaolin deposits of Yextho, located one km to the west of the geothermal manifestations. By the middle of the century, the area was already explored for geothermal energy, which resulted in the first geothermal power plant in all America, operating between 1959 and 1972 with a nominal capacity of 3.5 MW.The thermal manifestations of Pathe are located at the junction of two regional normal fault systems, striking N-S and E-W, and are hosted by a volcanic unit (tuff and lava) of basic to intermediate composition and Upper Miocene age. Surficial hydrothermal alteration is conspicuous and largely controlled by faults of these two systems. Associated with the N-S faults is a calcite-gypsum alteration assemblage, indicating oxidized, alkaline sulfate-rich hydrothermal fluids. On the other hand, linked to the later E-W faults are the kaolin deposits; they are the product of an advanced argillic alteration that is characteristic of a steam-heated environment and indicates acidic conditions (pH: 2 to 3) and temperatures around 100 °C. Because of its unambiguous relation to faults and the absence of recent (Quaternary) volcanism, Pathe is likely to be a fault-controlled geothermal system (non-magmatic, extensional domain type). The successive alteration events suggest that the hydrothermal activity is long-lived and dates back to before the Pliocene

Dinar Fault is an active breakaway fault that plays an essential role in the southwestern Anatolia extensional tectonic regime's neotectonic development. The Dinar Fault's seismicity was proven by October 1, 1995, Dinar Earthquake (Mw 6.2). It consists of three geometric segments called Gumussu, Kizilli and Dikici, respectively, from northwest to southeast. The October 1, 1995 Dinar Earthquake occurred on the Kizilli Segment, approximately 10 km long, located in the middle of the Dinar Fault. In this study, active tectonic and kinematic characteristics and paleoseismic history of the Dinar Fault were investigated. Based on the fault plane slip data obtained from the Dinar Fault, it is a normal fault with a minor right-lateral strike-slip component. A total of four trenches were excavated across the 1995 surface rupture. According to paleoseismological trench studies, the Dinar Fault's slip rate was estimated as 0.37–0.56 mm/year and the average earthquake recurrence interval was 523 years in the last 3660 years. A number of these earthquakes destroyed the ancient city of Apameia Kibotos (ancient Dinar). The last earthquake that occurred on the Dinar Fault is the October 1, 1995 Dinar Earthquake. The date of the penultimate event occurring on the Dinar Fault was determined as AD 1318–1486, while the antepenultimate event was determined as AD 916–1155. The oldest event occurring on the Dinar Fault was determined as AD 916–111 BC. Structural and paleoseismological data indicate that the other sub-segments of the Dinar Fault, which did not rupture in the 1995 earthquake, have the potential to produce earthquakes with magnitudes varying between Mw: 6.2 to Mw: 6.6.

[Abstract Normal faults grow either by radial propagation and segment linkage or by accruing displacement without a proportional increase in fault length. To test these competing models of fault growth, a novel 2D seismic stratigraphic interpretation of the recent Fucino Basin of the central Apennines (Italy) has been performed. The Fucino is a major Pliocene‐Quaternary non‐marine ‘extensional collapse basins’, developed immediately after the Apenninic compressional strain had locally abated, and bounded by seismogenic faults that generate strong (Mw = 6–7) and destructive earthquakes. The Fucino is an overall dual polarity half‐graben, built around two border fault systems: the northern one lies along the east‐northeast striking Avezzano‐Bussi regional fault‐zone; the other, south‐eastern trending, bounds the basin to the east. Two separate fault‐driven depocentres of fluvio‐lacustrine sequences (maximum thicknesses of ~1,750 m) are present. One is associated to the northern border faults, with mainly Late Pliocene activity; the second is to the hanging‐wall of the eastern border‐faults and reveals a stepwise Pleistocene‐Recent activity. Tectonic depocentres have migrated clockwise through time, and new‐born fault systems have developed at the south‐eastern basin periphery (Gioia dei Marsi area). This, together with the progressive accumulation of throw in time without significant fault lengthening, suggests that the model of fault growth by segment linkage is not the best explanation for this basin. Instead, the stepwise onset and growth of the Fucino extensional collapse faulting, and its ongoing earthquake hazard, may have been promoted by polyphase inversion tectonics of inherited deep‐seated zones of weaknesses (e.g. Avezzano‐Bussi Line)., The Fucino is an overall dual polarity half‐graben, built around two border fault systems: the northern one lies along the east‐northeast striking Avezzano‐Bussi regional fault‐zone; the other, south‐eastern trending, bounds the basin to the east. Two separate fault‐driven depocentres of fluvio‐lacustrine sequences (maximum thicknesses of ~1,750 m) are present. The northern border fault showed mainly a Late Pliocene activity; the eastern border‐faults reveal a stepwise Pleistocene‐Recent activity. Tectonic depocentres have migrated clockwise through time, and new‐born fault systems have developed at the south‐eastern basin periphery (Gioia dei Marsi area). This, together with the progressive accumulation of throw in time without significant fault lengthening, suggests that the model of fault growth by segment linkage is not the best explanation for this basin. ]

Normal faults are commonly segmented along strike, with segments that localize strain and influence propagation of slip during earthquakes. Although the geometry of segments can be constrained by fault mapping, it is challenging to determine seismically relevant segments along a fault zone. Because slip histories, geometries, and strengths of linkages between normal fault segments fundamentally control the propagation of rupture during earthquakes, and differences in segment slip rates result in differential uplift of adjacent footwalls, we used along-strike changes in footwall morphology to detect fault segments and the relative strength of the mechanical links between them.We applied a new geomorphic analysis protocol to the Wassuk Range fault, Nevada, within the actively deforming Walker Lane. The protocol examines characteristics of footwall morphology, including range-crest continuity, bedrock-channel long profiles, catchment area variability, and footwall relief, to detect changes in strike-parallel footwall characteristics. Results revealed six domains with significant differences in morphology that we used to identify seismically relevant fault segments and segment boundaries. We integrated our results with previous studies to determine relative strength of links between the six segments, informing seismic hazard assessment. When combined with recent geodetic studies, our results have implications for the future evolution of the Walker Lane, suggesting changes in the accommodation of strain across the region. Our analysis demonstrates the power of this method to efficiently detect along-strike changes in footwall morphology related to fault behavior, permitting future researchers to perform reconnaissance assessment of normal fault segmentation worldwide.

Rupture source directivity and its potential frequency dependence remains an open question in seismology, especially for small-to-moderate earthquakes. In this research, we first calibrate a non-ergodic empirical model of the acceleration Fourier Amplitude Spectra (FAS), and then we adapt our tool in Spectral Amplitude (SA). Thanks to the large amount of high-quality seismic recordings (consisting of more than 400 earthquakes from magnitude 3.4 to 6.5, 460 stations, thus involving more than 30’000 waveforms in the time frame 2008-2018), we provide a statistical overview based on empirical evidence of seismological observations in the Central Italy area, which represents a unique natural laboratory for earthquakes occurring on normal faults. The non-ergodicity enables to remove all the other components of variability (i.e. the event-, site- and path-related) in the ground motion model (GMM) and hence allowing to better isolate the effects connected to source-directivity, that are not unaccounted in the epistemic variability of the ground motion. According to our criteria, about 36% of the analyzed events (162 out of 456) exhibits directivity. The distribution of the rupture directions is aligned, as expected, with the strikes of the major faults of the Central Apennines. We find that the directivity is a band-limited phenomenon, which spans from corner frequency (fc) up to approximately 5 times the event’s fc; in case of not very pronounced directivity, this band tends to be narrow, suggesting that the complex rupture processes at high-frequency are mainly stochastic. Moreover, we observe directivity not only during seismic sequences, but also in background seismicity. Preliminary results provide a useful hint regarding directivity’s parameterization as a frequency-dependent band-limited phenomenon, to be implemented in future ground motion modeling and scenario’s predictions.

We present high-resolution mapping and surface faulting measurements along the Lost River fault (Idaho-USA), a normal fault activated in the 1983 (Mw 6.9) earthquake. The earthquake ruptured ~35 km of the fault with a maximum throw of ~3 m. From new 5 to 30 cm-pixel resolution topography collected by an Unmanned Aerial Vehicle, we produce the most comprehensive dataset of systematically measured vertical separations from ~37 km of fault length activated by the 1983 and prehistoric earthquakes. We provide Digital Elevation Models, orthophotographs, and three tables of: (i) 757 surface rupture traces, (ii) 1295 serial topographic profiles spaced 25 m apart that indicate rupture zone width and (iii) 2053 vertical separation measurements, each with additional textual and numerical fields. Our novel dataset supports advancing scientific knowledge about this fault system, refining scaling laws of intra-continental faults, comparing to other earthquakes to better understand faulting processes, and contributing to global probabilistic hazard approaches. Our methodology can be applied to other fault zones with high-resolution topographic data. Machine-accessible metadata file describing the reported data: https://doi.org/10.6084/m9.figshare.13198259

The extensional structure as a normal fault could be found in many places at the southern part of Java compressive tectonic regime. The research area is in the eastern part of the South Serayu Mountains. This normal fault structure is the boundary of the South Serayu Mountains at the eastern part with Kulon Progo Tertiary volcanic Mountains. In the field, these normal fault lineament zones create the Bogowonto river as a boundary of two different geological styles. The influence of this structure on the geological dynamic of the South Serayu Mountains and the Kulon Progo Mountains is important to be explained. The study was conducted by measuring and analyzing fault data and lithology that developed in the area around the two basins boundary. The distribution of the Kulon Progo volcanic rocks indicates the presence of the extensional fault structure. The volcanic facies distribution of the volcano is cut and becomes narrow in the west, while the northward is very wide. Normal fault striations analysis on the fault plane along the fault line shows the least stress trending west-northwest that has worked to create North-South normal faults. The fault-controlled by stress with the vertical main compression area. They have worked to create North Northeast-South Southwest (NNE-SSW) normal faults with westward dipping.

The Taupō Volcanic Zone (TVZ) is characterised by a negative residual gravity anomaly that correlates with a zone of normal faulting, subsidence and voluminous silicic volcanism from c. 2 Ma. A ste...

We used the audio magnetotelluric (AMT) method to delineate subsurface resistivity structures associated with the western Ilan Plain, which is emerged from the orogenic belt in northeastern Taiwan and is thought to be influenced by the opening Okinawa Trough. The most recent extension phase of the Okinawa Trough starting from approximately 0.1 Ma involved ENE- and WSW-trending normal faults off the Ilan Plain. Nevertheless, the region was originally a thrust-and-fold belt related to the subduction of the Philippine Sea Plate under the Eurasia Plate. Our study focuses on how the later opening of the Okinawa Trough has affected this previously compressional region. From the results of the AMT surveys, we found that the area features a series of N-S trending fracture zones in addition to the E-W normal fault systems. Comparing the AMT data with the data from seismic reflection profiles, we found that the normal fault systems are truncated by young strike-slip faults and modified the relief of the rock basement in a recent stage of formation. The western part of the study area is dominated by left-lateral strike-slip faults while the eastern part is dominated by right-lateral strike-slip faults. The findings drawn from our AMT resistivity images as well as from the reinterpreted seismic profiles constitute new evidence that the extrusion regime may have gradually taken over the regional stress state and reset the regional stress-strain conditions that was one dominated by the Okinawa extension in the western and southern part of the Ilan plain.

K-Ar dating of fault gouge from the intersection of the WNW-striking Ohika Detachment of the Paparoa Metamorphic Core Complex and a NNE-striking high-angle normal fault (Ohikaiti Fault) yielded an ...

A large number of landslide events have repeatedly struck the border zone of the northwestern plateaus of Ethiopia. Debre Sina area is one of the most tectonically active areas located along the western margin of the Afar depression, which is frequently affected by landslides. Despite that, urban and rural development is currently active in almost the entire area. It is crucial, therefore, to understand the main causes and failure mechanisms of landslides in the Debre Sina area and its surroundings. The present study investigated landslides using field mapping of geological and geomorphological features, remote sensing, geo-morphometric analysis, structural analysis, rainfall data, landslide inventory, and earthquake data. The results of the study indicate that large-scale and deep-seated landslide problems appear to be caused by complex geological settings and rugged topography. In particular, the location and morphology of the Yizaba Wein and Shotel Amba landslides are strongly controlled by geological structures. Their flanks are bounded by high angle faults, and their main basal failure surfaces have developed within a W–E striking eastward-dipping normal fault zone. The complex litho-structural and morphologic settings play a vital role in controlling the geometry of the slip surfaces and the stability of the landslides., Research School PLUS, Ruhr University Bochum (DE)

In the northwest of the Himalayan-Tibetan Orogen, the ∼250 km-long Kongur Shan extensional system in the eastern Pamir was formed during the convergence between the Indian and Asian plates. Tectonic activity of the Kongur Shan normal fault and the Tashkurgan normal fault can help to reveal the origin of east-west extension along the Kongur Shan extensional system. The Kongur Shan fault has been extensively studied, while the Tashkurgan fault calls for systemic research. In this study, low-temperature thermochronology including apatite fission track analysis and apatite and zircon (U-Th)/He analyses is applied to constrain the timing of activity of the Tashkurgan fault. Results indicate that the Tashkurgan fault initiated at 10−5 Ma, and most likely at 6−5 Ma. The footwall of the Tashkurgan fault has been exhumed at an average exhumation rate of 0.6−0.9 mm/a since the initiation of the Tashkurgan fault. Combined with previous research on the Kongur Shan fault, we believe that the origin of east-west extension along the Kongur Shan extensional system was driven by gravitational collapse of over-thickened Pamir crust.

This research aimed to identify the presence of faults in Taman Ayu Village, Gerung District, West Lombok Regency by mapping the magnetic field. The fault outcrops found near this location becomes the reason to suspected the fault existence that reaching residents, farming area and access roads, so it is necessary to study the type, depth and direction of the fault. Measurements were made on 11 lines with a length of each line is 3 km. Each line of measurement is 300 m apart from each other and the distance between measurement points is 50 m, 100 m, and 200 m depending on the distance from the target location. Separation between regional anomalies and residual anomalies using the upward continuation method at an altitude of 1000 m. Qualitative interpretation of residual anomalies results in low anomalies with values from -890.9 nT to 897.3 nT. Quantitative interpretation of the five cross sections by the inverse modeling method with Oasis Montaj 6.4.2 software resulting subsurface geological structures in the form of normal fault. This normal fault is at a depth of 30 m to 480 m which is composed of layers of silt, sandy silt, sand, clay and breccia. The fault passes through Gapuk Village, Taman Ayu and Kebon Ayu and passes through the highway in Northeast – Southwest direction

Urban tunnels crossing faults are always at the risk of severe damages. In this paper, the effects of a reverse and a normal fault movement on a transversely crossing shallow shotcreted tunnel are investigated by 3D finite difference analysis. After verifying the accuracy of the numerical simulation predictions with the centrifuge physical model results, a parametric study is then conducted. That is, the effects of various parameters such as the sprayed concrete thickness, the geo-mechanical properties of soil, the tunnel depth, and the fault plane dip angle are studied on the displacements of the ground surface and the tunnel structure, and on the plastic strains of the soil mass around tunnel. The results of each case of reverse and normal faulting are independently discussed and then compared with each other. It is obtained that deeper tunnels show greater displacements for both types of faulting.

This paper presents a series of model tests on geosynthetic-reinforced soil (GRS) foundations across a normal fault. The aim was to evaluate the performance of reinforced foundations as a mitigation measure for surface faulting hazards. Experimental tests modeled a 3-m thick foundation in prototype subjected to a fault displacement up to 90 cm. Test variables included the number of reinforcement layers, reinforcement stiffness and location, and foundation height. Digital image analysis techniques were applied to determine the ground settlement profile, angular distortion, shear rupture propagation, and mobilized reinforcement tensile strain at various magnitudes of fault offset. Test results revealed that compared with the unreinforced foundation, reinforcement inclusion could effectively prevent the shear rupture propagating from the bedrock fault to the ground surface. It also spread the differential settlement to a wider influential zone, resulting in an average reduction of 60% in the fault-induced angular distortion at the ground surface. The maximum angular distortion decreased as the foundation height, number of reinforcement layers, and reinforcement stiffness increased. Relationships between the maximum angular distortion and maximum mobilized reinforcement tensile strain with fault displacement were therefore established. Based on the findings from this study, design suggestions and implications are discussed.

To analyze the generation of different ground fissure disasters, two typical ground fissures were selected. With geological survey and exploration data, the spatial characteristics of the Songzhuang and Gaoliying fissures were investigated. The different occurrence factors for the Songzhuang and Gaoliying fissures were analyzed based on geological structure and groundwater. The conclusions contain are as follows. The affected body of the Songzhuang fissure exhibits obvious tensile deformation, and it is not contact with buried faults. The fracture-affected body of the Gaoliying fissure shows obvious vertical dislocation and shear, and this is compounded with buried faults. The distribution characteristic of the Songzhuang fissure was controlled by the tectonics and the normal fault, while the buried fault not only control the distribution feature of the Gaoliying fissure but also controlled its deformation characteristic. A buried fault is the geological background for the formation of the Gaoliying fissure. The long-term exploitation of groundwater has caused the horizontal deformation of the soil and the rigid rotation of stratum in the subsidence edge. Both of them are the reason for the tensile deformation. Due to the activities of buried faults and differential subsidence in small areas, the affected bodies of the Gaoliying fissure showed vertical dislocation and shear deformation.

Mountain tunnel crossing a normal fault in seismically active zone is easily affected by normal fault slip and earthquake. It is necessary to study tunnel dynamic response under action of normal fault slip and earthquake. In this paper, a three-dimensional normal fault sliding device was designed, and a shaking table test was carried out to study tunnel seismic performance under normal fault slip. The results show that peak acceleration of lining is dominated by an existence of fault and direction of seismic excitation, not normal fault slip. And the incremental strains of lining in critical zone with 1.7 times fault thickness and centered in faults induced by normal fault slip and seismic excitation are larger than ones only by seismic excitation. And the incremental strains in critical zone increase with the increase of normal fault slip magnitude ranging from 0 to 2 mm. And normal fault slip results in a significant reduction of overall tunnel stiffness subjected to an earthquake. These experimental results provide a scientific reference for prevention and control measurement of tunnel damage under earthquake and normal fault slip.

The identification and characterisation of faults in urban environments is important to inform seismic and landslide hazard, yet urban development often obscures geological and geomorphological evi...

International audience; Sedimentary breccias deposited on a talus slope during extension at the front of a normalfault or at the base of a slope are related to the creation of substantial topography. The architectureof talus slopes resulting from exhumation during extension is different from that of rock cliffs withoutdeformation. In this work, we run several analogue models, with or without extension, in order toanalyse the external geometry and internal organization of sedimentary breccias and their evolutionin time and space. This temporal organization of the sand layers in the experiments shows that normalunroofing sequences are characteristic of progressive exhumation and continuous deformation duringextension, whereas reverse unroofing is related to cliff destruction without vertical movement. Inthe experiment with wet layers of sand, the blocks that resulted from the aggregates of sand grains aregenerally deposited farther away than single sand grains and are located at the base of the slope; thisis one of the main characteristics of rockfalls. The analogue results are compared to natural examples; Les brèches sédimentaires déposées sur un talus d’éboulis pendant l’extension au frontd’une faille normale ou à la base d’un versant abrupt sont liées à la création d’une topographie importante.L’architecture des talus d’éboulis résultant de l’exhumation pendant l’extension est différentede celle des falaises rocheuses sans déformation. Dans ce travail, nous avons réalisé plusieursmodèles analogues, avec ou sans extension, afin d’analyser la géométrie externe et l’organisation internedes brèches sédimentaires et leur évolution dans le temps et l’espace. L’organisation temporelledes couches de sable dans les expériences montre que la séquence de dépôt normale est caractéristiqued’une exhumation progressive et d’une déformation continue pendant l’extension, alors qu’uneséquence de dépôt inverse est liée à la destruction de la falaise sans mouvement vertical. Dans les expériences réalisées avec des couches de sable humide, les blocs résultant des agrégats de grains desable sont généralement déposés plus loin que les grains de sable individuels et sont situés à la base dela pente; c’est l’une des principales caractéristiques des éboulements. Les résultats des modélisationssont comparés à des exemples naturels.

El análisis morfotectónico del sector central del Promontorio Balear, entre las islas de Ibiza y Mallorca, mediante batimetría multihaz y perfiles sísmicos de muy alta resolución ha permitido diferenciar varios rasgos morfológicos relacionados con la tectónica a dos escalas. Los elementos de gran escala, de dirección NE-SO, son: i) el escarpe Émile Baudot; ii) el monte submarino Émile Baudot, y iii) la alineación de montes submarinos Ausiàs March y Ses Olives. Los elementos de pequeña escala son: i) dos elevaciones longitudinales (ENE-OSO); ii) escarpes rectilíneos (NO-SE a NE-SO); iii) depresiones tectónicas (NNE SSO a NE-SO); y iv) alineaciones rectilíneas de pockmarks (NO-SE a NNE-SSO). Los elementos de mayor tamaño responden a la configuración estructural neógeno-cuaternaria. El escarpe Émile Baudot limita el Promontorio Balear y la cuenca oceánica del Mediterráneo Occidental. La alineación de montes submarinos Ausiàs March y Ses Olives está generada por una fase extensional, y el monte submarino Émile Baudot forma parte de una alineación volcánica NO-SE asociada a la Zona de Fractura de Ibiza. Los elementos de pequeña escala están relacionados con estructuras tectónicas activas que deforman las unidades sedimentarias del Cuaternario y el fondo marino. Las elevaciones longitudinales están generadas por pliegues anticlinales, mientras que el resto de estructuras están asociadas a la actividad de fallas normales de buzamiento alto., A morphotectonic analysis has been carried out between the islands of Ibiza and Majorca in the central sector of the Balearic Promontory using multibeam bathymetry and very high-resolution seismic profiles. Several morphological features related to tectonics at two different scales have been differentiated. The large-scale features have a NE-SW direction, they are: i) the Émile Baudot Escarpment; ii) the Émile Baudot seamount, and iii) the Ausiàs March and Ses Olives seamounts alignment. The differentiated small-scale elements are i) two longitudinal elevations (ENE-WSW); ii) rectilinear scarps (NW-SE to NE-SW); iii) tectonic depressions limited by one or two scarps (NNE-SSW to NE-SW), and iv) rectilinear pockmarks alignments (NW-SE to NNE-SSW). The largest elements respond to the Neogene-Quaternary structural configuration. The Émile Baudot escarpment is the limit between the Balearic Promontory and the Western Mediterranean oceanic basin. The alignment of the Ausiàs March and Ses Olives seamounts respond to the last extensional phase, and the Émile Baudot seamount forms part of a NW-SE volcanic alignment that could be associated with the Ibiza Fracture Zone. The smaller elements are related to active tectonic structures that deform Quaternary sedimentary units and the seafloor. The longitudinal elevations correspond to anticlinal folds, while the rest of the structures are associated to the activity of near vertical normal faults., Proyecto INTEMARES. Sub-acción A.2.2: Mejora del conocimiento para la declaración de nuevos espacios marinos por su importancia para hábitats. Montes submarinos del Canal de Mallorca: Emile Baudot, Ses Olives y Ausias March, INTEMARES_A22_B

Surface faulting earthquakes are known to cluster in time from historical and palaeoseismic studies, but the mechanism(s) responsible for clustering, such as fault interaction, strain-storage, and evolving dynamic topography, are poorly quantified, and hence not well understood. We present a quantified replication of observed earthquake clustering in central Italy. Six active normal faults are studied using 36Cl cosmogenic dating, revealing out-of-phase periods of high or low surface slip-rate on neighboring structures that we interpret as earthquake clusters and anticlusters. Our calculations link stress transfer caused by slip averaged over clusters and anti-clusters on coupled fault/shear-zone structures to viscous flow laws. We show that (1) differential stress fluctuates during fault/shear-zone interactions, and (2) these fluctuations are of sufficient magnitude to produce changes in strain-rate on viscous shear zones that explain slip-rate changes on their overlying brittle faults. These results suggest that fault/shear-zone interactions are a plausible explanation for clustering, opening the path towards process-led seismic hazard assessments.

Upper-plate normal faults along forearcs often accumulate slip during >Mw 6 earthquakes. Such normal faults traverse the forearc of the Hellenic Subduction System (HSS) in Greece and are the focus of this study. Here, we use detailed field-mapping and analysis of high-resolution Digital Elevation Models (DEMs) to study 42 active normal faults on the islands of Kythira and Antikythira in the Aegean Sea. Onshore fault kinematic data are complemented by seabed bathymetry mapping of ten offshore faults that extend along the Kythira-Antikythira Strait (KAS). We find that normal faults in the KAS have lengths of ∼1–58 km and scarps ranging in height from 1.5 m to 2.8 km, accommodating, during the Quaternary, trench-orthogonal (NE-SW) extension of ∼2.46 ± 1.53 mm/a. Twenty-eight of these faults have ruptured since the Last Glacial Maximum, with their postglacial (16 ± 2 ka) displacement rates (0.19–1.25 mm/a) exceeding their Quaternary (≤0.7–3 Ma) rates (0.03–0.37 mm/a) by more than one order of magnitude. Rate variability, which is more pronounced on short (

The quantitative morphology of bedrock fault surfaces combined with aerial surveys and field identification is a useful approach to identify paleoearthquakes, obtain coseismic slips, and evaluate the seismogenic capacity of active faults in bedrock areas where traditional trenching methods are not applicable. Here, we report a case study of the Jiaocheng Fault (JCF) in the Shanxi Rift, China. Although several studies have been conducted on the JCF, its coseismic slip history and seismogenic capacity are still unclear. To address these problems, we investigated two bedrock fault surfaces, Sixicun (SXC) and Shanglanzhen (SLZ), on the JCF’s northern segment using quantitative morphological analysis together with aerial and field surveys. Quantitative fractal analysis based on the isotropic empirical variogram and moving window shows that both bedrock fault surfaces have the characteristics of vertical segmentation, which is likely due to periodic earthquakes, the coseismic slip of which can be determined by the height of the segments. Three seismic events at SXC, with a coseismic vertical slip of 1.74, 1.65, and 1.99 m, and three seismic events at SLZ, with a coseismic vertical slip of 1.32, 2.35, and 1.88 m, are identified. Compared with the previous studies, these three seismic events may occur in the Holocene, but it requires absolute dating ages to support, which is also the focus of our future work. Considering the seismologic capability (M>7.5) and the relationship between the recurrence interval of ~2.6 kyr and elapsed time of more than 3 kyr, the seismic hazard of the northern and middle segments of the JCF requires immediate attention.

Based on the interpretation of 2D seismic profiles integrated with surface geological investigations, a mechanism responsible for the formation of a large scale normal fault zone has been proposed. The fault, here referred to as the Rycerka Fault, has a predominantly normal dip-slip component with the detachment surface located at the base of Carpathian units. The fault developed due to the formation of an anticlinal stack within the Dukla Unit overlain by the Magura Units. Stacking of a relatively narrow duplex led to the growth of a dome-like culmination in the lower unit, i.e., the Dukla Unit, and, as a consequence of differential uplift of the unit above and outside the duplex, the upper unit (the Magura Unit) was subjected to stretching. This process invoked normal faulting along the lateral culmination wall and was facilitated by the regional, syn-thrusting arc–parallel extension. Horizontal movement along the fault plane is a result of tear faulting accommodating a varied rate of advancement of Carpathian units. The time of the fault formation is not well constrained, however, based on superposition criterion, the syn -thrusting origin is anticipated.

This study reports on the cosmogenic 36Cl dating of two normal fault scarps in western Turkey, that of the Manastır and Mugırtepe faults, beyond existing historical records. These faults are elements of the western Manisa Fault Zone (MFZ) in the seismically active Gediz Graben. Our modeling revealed that the Manastır fault underwent at least two surface ruptures at 3.5 ± 0.9 ka and 2.0 ± 0.5 ka, with vertical displacements of 3.3 ± 0.5 m and 3.6 ± 0.5 m, respectively. An event at 6.5 ± 1.6 ka with a vertical displacement of 2.7 ± 0.4 m was reconstructed on the Mugırtepe fault. We attribute these earthquakes to the recurring MFZ ruptures, when also the investigated faults slipped. We calculated average slip rates of 1.9 and 0.3 mm yr−1 for the Manastır and Mugırtepe faults, respectively., Geosciences, 11 (11), ISSN:2076-3263

National audience; This study focuses on breccias, widely developed in the Bas Agly syncline at the LateJurassic/Early Cretaceous boundary. Both their age and formation processes aredebated and remained hypothetical until today.According to our detailed sedimentological study, the breccia localized in the LateJurassic are spatially associated with large-throw normal faults and show a clearsedimentary character. They result from the creation of a steep topography thatbecomes unstable, producing major rockfalls. The studied breccias, are characterizedby poorly sorted polygenic deposits of pebbles to boulders composed of highly angularpluri-millimetric to pluri-metric carbonate clasts. A lateral evolution is observed, withpebble-size clasts found near the normal fault and boulder-size clasts away from thefault. This evolution is related to the rockfall process as the total kinetic energy acquiredby the small clasts during the fall is lower than that acquired by the bigger ones; as aresult, the latter are able to travel farther. These breccias are related to a first stage ofextension during the Late Jurassic and marks the beginning of the Early Cretaceousextension. However, the heterogeneity and complexity of the structure of carbonatebreccias require a detailed characterization of both their petrographic evolution anddiagenetic paleoenvironment in order to confirm our sedimentological model.Based on observations under S.E.M, polarized-light and fluorescence microscopy adetailed inventory of the diagenetic phases has been performed. From these analyses, adiagenetic sequence and a chronology of the cements have been reconstructed, usingprinciples of overlapping, superposition and inclusion. The oxygen and carbon isotopiccompositions of some cements and matrices of these breccias allowed to specify thediagenetic environments.The occurrence of metamorphic minerals overprinting the latest phase of calcitecementation strongly suggests that the breccia deposited prior to the Albo-Cenomanianregional metamorphic phase in contrast to previous stratigraphic attributions (Eoceneage) and support our interpretation of an interstratified sedimentary breccia of LateJurassic age. Thus, it is crucial to know the real age of these rocks. In order to solve thisissue, we initiated a geochronological study, using in-situ U-Pb dating by LA-ICP-MSand focusing on the carbonate matrix of the breccias. This approach has provensuccessful and yielded ages consistent with the proposed depositional environment.

International audience

Normal fault linkage has significant impacts on uplift patterns and erosional processes in extensional regions. However, geomorphic process-based constraints on landscape response to normal fault linkage are still scarce. Here, we use landscape evolution models to examine how a landscape responds to the linkage of two normal faults. The results demonstrate that topography dynamically responds to the changes in uplift patterns that accompany fault linkage. Specifically, our results indicate that after fault linkage, (1) the steepest topography and the highest erosion rate shift from the center of each fault segment to the linkage zone; and (2) the main drainage divide evolves from an M-shape to a bow-shape. We apply these findings to the Langshan Mountains in northern China, and suggest that the two piedmont fault segments have linked and that a high geohazard risk exists near the linkage zone, where the steep, transient topography is experiencing intense erosion.

In this paper, we explored the relationship between the stream-length gradient index over the Kiulu River upstream and its respective landform. The knickpoints derived from stream-length gradient index detected sudden drop in elevation that may be associated with recent tectonic activity over NW Sabah. To illustrate the changes in the stream profile, two knickpoints, F1 which coincided with historical earthquakes, and F2 which showed peak anomaly are selected. The landform over knickpoint F1 showed river diversions whereas the landform over knickpoint F2 showed deep ponding. Both field sites, however showed consistent alternation between rapids and ponding forming a step-like landform where the inferred normal fault is oriented at N40E. The stretched landform over the Kiulu river sites supports an extension setting that may be associated with gravity-sliding tectonics over NW Sabah.

The main goal of this study is introducing a novel fault current limiter based on parallel resonance structure (PRFCL) for high voltage application. During normal mode, the PRFCL reactor is short-circuited via a rectifier bridge DC output voltage and LC resonance tank shows negligible impedance in the line. During a fault, the rectifier bridge switches are turned off, so that the parallel resonance LC tank connects to the line with high impedance. This impedance of the resonance structure can limit the fault current, successfully. It is shown that the suggested PRFCL can act as a breaker and opens the line during the fault period. In order to show the suggested PRFCL abilities, MATLAB software is used to simulate the normal and fault cases. In addition, a scale-down prototype is implemented to confirm the simulation results. The comparative study shows that PRFCL has acceptable performance in normal and current limiting operation modes.

Purpose. Investigation of the conditions peculiarities of occurrence and rupture deformations of sandstones in outcrops along the right bank of the river Kazenny Torets in the field of the mine “Capital”. Methodology. In this work there were used: traditional structural-geological methods of field research; methods of field tectonophysical research; computer programs “Fabric-8” and “Win-Tensor” for processing field data, building of the stretch rose-diagrams of rupture deformations and reconstructing paleostress fields. Results. The conditions of occurrence of sandstones and their changes in space have been investigated. The systems of tectonic fractures, their mineral filling and influence on the material composition of the sedimentary rocks have been studied. Special tectonophysical studies have been carried out to determine the signs of paleostress fields of different kinematic types and ages.Reconstruction of paleostress fields was carried out using the elements of beding of cracks, grooves and slip lines on their slide mirrors. Several systems of rupture dislocations have been identified based on the results of studies in the hanging wing of the Glubokoyarsky fault. Systems of cracks have been identified, which facilitated the migration of deep-seated solutions with iron compounds. Such solutions changed the composition of sandstones in the wings of ruptured dislocations and formed zones of rock saturation with iron hydroxides up to 10 cm thick. Scientific novelty. For the first time in the outcrops on the day surface in sandstones of the hanging wing of the Glubokoyarsk fault, systems of tectonic fault dislocations of higher orders have been established. The repeated tectonic activation of the Glubokoyarsk normal fault in fields of paleostresses of different kinematic types has been established. The influence of ruptured dislocations on the formation of accumulations of iron hydroxides in rocks has been studied. Practical significance. The features of the conditions of occurrence of sandstones and the system of faulting dislocations in the hanging wing of the Glubokoyarsky fault have been established, which make it possible to predict the structural-geological, tectonic and tectonophysical conditions near fault dislocations, which is important for planning and carrying out mining operations in mine fields. Key words: sandstones, fault, tectonic cracks, iron hydroxides, reconstruction, paleostress field.

Many low-angle normal faults (dip ≤30°) accommodate tens of kilometers of crustal extension, but their mechanics remain contentious. Most models for low-angle normal fault slip assume vertical maximum principal stress σ1, leading many authors to conclude that low-angle normal faults are poorly oriented in the stress field (≥60° from σ1) and weak (low friction). In contrast, models for low-angle normal fault formation in isotropic rocks typically assume Coulomb failure and require inclined σ1 (no misorientation). Here, a data-based, mechanical-tectonic model is presented for formation of the Whipple detachment fault, southeastern California. The model honors local and regional geologic and tectonic history and laboratory friction measurements. The Whipple detachment fault formed progressively in the brittle-plastic transition by linking of “minidetachments,” which are small-scale analogs (meters to kilometers in length) in the upper footwall.Minidetachments followed mylonitic anisotropy along planes of maximum shear stress (45° from the maximum principal stress), not Coulomb fractures. They evolved from mylonitic flow to cataclasis and frictional slip at 300–400 °C and ∼9.5 km depth, while fluid pressure fell from lithostatic to hydrostatic levels. Minidetachment friction was presumably high (0.6–0.85), based upon formation of quartzofeldspathic cataclasite and pseudotachylyte. Similar mechanics are inferred for both the minidetachments and the Whipple detachment fault, driven by high differential stress (∼150–160 MPa). A Mohr construction is presented with the fault dip as the main free parameter. Using “Byerlee friction” (0.6–0.85) on the minidetachments and the Whipple detachment fault, and internal friction (1.0–1.7) on newly formed Reidel shears, the initial fault dips are calculated at 16°–26°, with σ1 plunging ∼61°–71° northeast. Linked minidetachments probably were not well aligned, and slip on the evolving Whipple detachment fault probably contributed to fault smoothing, by off-fault fracturing and cataclasis, and to formation of the fault core and fractured damage zone.Stress rotation may have occurred only within the mylonitic shear zone, but asymmetric tectonic forces applied to the brittle crust probably caused gradual rotation of σ1 above it as a result of: (1) the upward force applied to the base of marginal North America by buoyant asthenosphere upwelling into an opening slab-free window and/or (2) basal, top-to-the-NE shear traction due to midcrustal mylonitic flow during tectonic exhumation of the Orocopia Schist. The mechanical-tectonic model probably applies directly to low-angle normal faults of the lower Colorado River extensional corridor, and aspects of the model (e.g., significance of anisotropy, stress rotation) likely apply to formation of other strong low-angle normal faults.

The 1983 Mw 6.9 Borah Peak earthquake generated ∼36 km of surface rupture along the Thousand Springs and Warm Springs sections of the Lost River fault zone (LRFZ, Idaho, USA). Although the rupture is a well-studied example of multisegment surface faulting, ambiguity remains regarding the degree to which a bedrock ridge and branch fault at the Willow Creek Hills influenced rupture progress. To explore the 1983 rupture in the context of the structural complexity, we reconstruct the spatial distribution of surface displacements for the northern 16 km of the 1983 rupture and prehistoric ruptures in the same reach of the LRFZ using 252 vertical-separation measurements made from high-resolution (5–10-cm-pixel) digital surface models. Our results suggest the 1983 Warm Springs rupture had an average vertical displacement of ∼0.3–0.4 m and released ∼6% of the seismic moment estimated for the Borah Peak earthquake and

The mobile south flank of Kīlauea Volcano hosts two normal fault systems, the Koa'e fault system (KFS) and the Hilina fault system (HFS). In historical time, at least three M>6.5 earthquakes have occurred on the basal detachment of the Kīlauea Volcano's south flank, with the most recent being the 4 May 2018 M6.9 earthquake. Here we analyze kinematic Global Positioning System data collected from 2001 to 2017 and interferometric synthetic aperture radar data before, during, and after the 2018 M6.9 earthquake to determine the crustal motion across the HFS and KFS faults. Our results indicate that the HFS faults did not significantly slip during the interseismic period from 2007 to 2011. Despite its substantial magnitude, interferometric synthetic aperture radar (InSAR) data show that the 2018 M6.9 earthquake triggered subcentimeter level slip along sections of the previously mapped HFS branches. Up to 20 cm of offset occurred on what appears to be a newly formed (or previously unknown) fault near the eastern end of the HFS. During the 3 months following the M6.9 earthquake, up to ~30 cm of slip occurred along the KFS, which helps accommodate rapid large‐scale subsidence of Kīlauea's summit region as large volumes of summit reservoir magma fed the lower East Rift Zone eruption. The HFS appears to activate only in concert with large earthquakes on the basal detachment. The KFS, on the other hand, moves both seismically during small local earthquakes and aseismically in response to nearby earthquakes and caldera subsidence.

Normal faulting earthquakes rarely rupture the entire extent of active normal faults, and can also jump between neighbouring faults. This confounds attempts to use segmentation models to define the likelihood of future rupture scenarios. We attempt to study this problem comparing the offsets produced in single earthquakes with those produced by multiple earthquakes over longer timescales, together with detailed studies of the structural geology. We study the active normal fault system that caused the Mw 6.3 2009 L'Aquila earthquake in central Italy, comparing the spatial distribution of coseismic offsets, cumulative offsets that have developed since 15 ± 3 ka, and the total offsets that have accumulated since the faults initiated at 2–3 Ma. Our findings suggest that: 1) faults within a segmented fault system behave as a single interacting fault segment over time periods including multiple earthquake cycles (e.g. 2–3 Ma or 15±3ka), with single earthquakes causing either partial or total ruptures of the entire system; 2) an along-strike bend causes throw and throw-rates enhancements within the bend throughout the seismic history of the fault system. We discuss the synchronised and geometrically controlled activity rates on these faults in terms of the propensity for floating earthquakes, multi-fault earthquakes, and seismic hazard.

The purpose of the present paper is to investigate the effects of a normal fault rupture propagation towards a highway embankment founded on a single-layered soil. To achieve this, quasi-static parametric numerical analyses are performed with the 2D finite difference code, FLAC. The work addresses the influence of the embankment's presence on the fault rupture path, as well as, the deformation of the embankment and the alteration of its initial compaction degree due to the rupture propagation. Results of numerical analyses indicate that the presence of embankment significantly affects the deformations of ground surface. In addition, it is observed that spread of normal fault rupture through the examined embankment causes substantial deformations of embankment's external surface and significant drop of relative compaction. This work achieves to map and quantify the damage of the embankment and therefore provides substantial information on its functionality and safety.

The lateral sealing ability of a normal fault is a major factor in creating hydrocarbon traps. Therefore, a methodology for assessing the sealing ability of faults in the siliciclastic sequences of subsidence basins has been established; moreover, by using this methodology, the uncertainty inherent in hydrocarbon exploration can be decreased. Moreover, the petrophysical properties of fault rocks and reservoirs are emphasized by the methodology. In addition, the petrophysical properties of fault rocks and reservoirs are mainly determined based on clay contents and compaction pressure according to experiments on manmade rock samples which are representative of the researching area. Furthermore, by using this methodology, the petrophysical properties of fault rocks and reservoirs, which are mainly determined based on clay content and compaction pressure according to experiments on manmade rock samples representative of the researching area are emphasized. Thus, the lateral sealing ability of the fault can be assessed as follows: First, a best-fit equation describing the displacement pressures, clay contents, and compaction pressures of the rock samples is established by us. Then, the positive pressure on the fault plane from the decomposition of effective overburden pressure is calculated; afterwards, the clay content of the fault rock (Shale Gouge Ratio) is calculated by us. Finally, the displacement pressures of the fault rock and the juxtaposed reservoir rock are predicted. Ultimately, based on this study which has been carried out, the results for the case study of the Tangjiahe fault in Well Gang 64, in the western part of the Qikou Sag, China coincide with the exploration results, which this coincidence confirms that this methodology is capable of evaluating the lateral sealing ability of faults in certain geologic settings.

The geometry of faults exposed in the field is at least partly controlled by host-rock lithology. However, little work has been published on the effect of lithology on the geometry of very large faults imaged in seismic data. This paper presents such a study for seismic-scale faults in the Norwegian Barents Sea. Gamma-ray data are used to extract clay volumes of the host rock. These clay volume logs are used to populate 3D seismic cubes with lithology information. Finally, the clay volume cubes are co-rendered with seismic coherence cubes using opacity blending. This makes it possible to visualize both lithology information and fault geometries in the same volume. Intervals of different lithologies are studied in order to compare fault geometries. The results show some differences between claystone-rich intervals and the more sandstone-dominated intervals. The fault zone is more segmented and wider in the claystones, while the sandy intervals are narrower and more localized with less segmentation. Larger displacement faults penetrate into deeper stratigraphic levels than smaller displacement faults, and their basal tips are unrelated to lithological decoupling.

In this study, centrifuge model tests and numerical analyses were conducted to investigate the deformation mechanisms of an existing tunnel due to normal faulting in sand. With the presence of a tunnel in sand stratum, normal faulting-induced ground surface settlements above the existing tunnel were significantly reduced (i.e., shielding effects). These shielding effects provide by the existing tunnel were decreased with the tunnel burial depth. When a kinematically constrained boundary condition was applied in the tunnel, the induced longitudinal strains at the tunnel crown were much larger than those observed in a tunnel with a free boundary condition.

Normal faults grow by either simultaneous increase in displacement and length (isolated model), or by rapid establishment of their final length before accumulating significant displacement (constant-length model), or a combination of these tow end-members. In this study, we integrate stratigraphic and structural observations with throw backstripping and time thickness maps to define the growth processes of a basin-bounding normal fault in the northern Polhem Subplatform, SW Barents Sea. During the initial 15 My of Early Cretaceous rifting, the fault system consisted of at least five en-echelon segments, which were ca. 5–10 km long. Throw backstripping indicates that fault segments were hard-linked after this initial stage to form a single 40 km long fault zone. Fault linkage resulted in displacement redistribution, with the locus of faulting being shifted from the center of each paleo-segment, to the center of the through going fault. Across fault incised valleys provide additional information on the topographic response to fault growth. Major valley incisions at the fault linkage zones outline the extent of the individual fault segments and support early isolated fault growth. Fault backstripping results suggest that valley incision and sedimentation rates kept up with fault slip rate, such that the incised valleys remained unaffected by the uplift of the latter fault linked stage. This study illustrates the importance of integrating stratigraphic and structural observations when reconstructing the evolution of basin-bounding normal faults. In particular, syn-rift erosional features, sediment thickness variations, sediment distribution, stratal geometries and onlap/truncation relationships are critical for estimating the growth of these structures.

Detailed structural analysis of an onshore field was carried out to study the geometry and interactions of the interpreted normal faults. The faults have E-W strike and are dipping towards the south. Majority of the faults are coherently linked with only a few displaying isolated growth model. Throw generally increases with increasing depth. The distribution of the throw on the fault planes shows different geometries ranging from symmetrical with steep gradients at the fault tips and displacement maxima at the center to asymmetrical with steep gradient at one tip. Faults interacted by way of splay and systematically formed relay ramp structures. At depth, splay display isolated fault profile rather than a maxima at the intersections suggesting an unusual interaction at intersection between major fault and splay with low displacement at intersection.