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Understanding fault zone dynamics in multi-scale is important to embrace the complexity of the earthquake behavior and its natural system. However, the opportunity to map and observe the fault zone behavior at depth with high spatial resolution are rare as also the challenge itself on targeting and identifying the fault zone at depth. We placed a 3D cross-fault fiber array with a downhole loop from surface to depth of 700m for Hole-A (Hanging wall site, crossing fault at depth), after drilling and coring to a frequent slip fault, Milun fault in a plate boundary zone, which ruptured during the 6 February 2018 Mw6.4 Hualien earthquake, and resulted in severe damage to several tall buildings with tens of casualties and injuries. Then, the surface segment crosses the surface fault rupture zone using commercial fiber, and to another downhole loop of 500m fiber for Hole-B (Footwall site). The high spatial resolution from distributed acoustic sensing (DAS) allows us to characterize the fault zone feature together with the retrieved core and geophysical logs after drilling through this frequent slip zone. This 3D route includes the experiment of using commercial fiber to the future application of surface rupture zone identification for seismic hazard mitigation. The project successfully retrieved the fault core associated with Milun fault zone, which could be also seen in geophysical logs with low velocity and resistivity, and mapped using Optical Fiber Sensing technique of the downhole fiber. Within the Milun fault zone, while a 20m thick fault core with grey and black gouge was discovered, a distinct seismic feature associated with this 20m fault gouge was found by its amplification of the strain records from DAS. This amplification ratio is about 2.5-3 when compared to the channels at deeper depth related to a consolidated rock material. This amplification factor was frequency and azimuth independently, as genuinely observed from all events (e.g. local, and teleseismic earthquakes) with similar amplification factor. Our study shows that the amplification from this 20m fault gouge zone is mainly from the nature of the heterogeneous medium in elastic constant while crossing the fault zone, especially the fault core. Similar feature at surface but with wider surface rupture zone (~ 200m) was found in DAS data as well although less evidence using commercial fiber, while could be validated from the densely deployed geophones crossing the surface rupture of the 2018 Hualien earthquake. Through the depth, a high-resolution asymmetric feature of this active fault was evidenced from the downhole optical fiber and cores. This fault zone behavior would be hardly seen or confirmed without continuous viewing of the wavefields to this high spatial resolution to meter scale. Although the narrow fault gouge, the nature of its amplification in strain due to its strong material contrast from fault gouge was intriguing, and requires intensive attention to consider the contribution of the fault zone heterogeneity in the medium. This might give hints on the understanding of the observation of earthquake dynamics triggering reported worldwide after the occurrence of a mega-earthquake.

The 2013 Ruisui earthquake is the first unequivocal evidence of the seismicity activity of the Central Range Fault (CRF) in the central Longitudinal Valley in Taiwan, and hence reveals the existence of aseismic slip on the CRF. The finite-fault coseismic model obtained from the Bayesian joint inversion of GNSS and strainmeter data suggests that the rupture area is mainly distributed on a 26 km × 22 km fault plane located at the depth of 3 to 19 km with a maximum slip of about 0.5 m. A variational Bayesian independent component analysis (vbICA) technique is applied to the detrended GNSS time series to extract postseismic deformations in the near-source region. Although the afterslip distribution was not able to be well inverted due to the lack of observation on the western side of the fault plane, using rate-and-state friction rheology to simulate the surface displacements generated by the stress-driven afterslip model, we infer for the first time the existence of a shallow velocity-strengthening region on the CRF, which is capable of hosting and sustaining aseismic transient deformations over months.

In this study, we conduct a multi-disciplinary study, including geophysics, geochemistry, and geology, in an attempt to reconstruct geothermal geological model(s) at the shallow 3 km, for a project of potential geothermal power generation at the Hongchailin site in the Ilan plain of northeastern Taiwan. Our geophysical techniques include seismic imaging from natural earthquakes as well as ambient noise. Three seismic arrays deployed at different time periods in the past decade were used. We also incorporate geophysical imaging results from previous studies, in particular a series of seismic reflection profiles. For the magnetotelluric (MT) technique, two major surveys have been conducted, including 2015-2018 AMT by National Central University and 2021-2022 MT by GERD and Academia Sinica. Three test holes were drilled around the Hongchailin site in 2016-2019. Logging and on-site measurements were conducted at increment depths, including stratigraphy and rock types, P/T measurements, fractures analyses, geochemical analyses (e.g., hydrogen/oxygen/helium isotope, fluid inclusion, etc.), and so on. Based on regional geology and structures, and incorporating geophysical subsurface imaging, we reconstruct geothermal geological models in line with detailed geological cross sections at the shallow 3 km level. We interpret that there exits a shallow geothermal reservoir within the massive quartz sandstone layers (Szeleng sandstone) at 1-2 km depth with the downhole temperature of 80-100 C. Geologically, the reservoir is located at the regional Songlo syncline and its south limb; and geophysically, it corresponds to a relatively low resistivity area. Isotope results show that the cool meteoric water came from nearby higher altitude mountain area, then flew through the Szeleng sandstone, which plunges 1-2 km depth below the Ilan plain. Hot fluid is interpreted to be derived from deeper heat source and to be upflowed along a N-S trending vertical faults system near the Hongchailin area. In addition, two E-W trending major faults, identified by the seismic reflection profiles, seem to be acted as hydrothermal fluid barriers to confine the hot fluid within the reservoir area.

The Ilan Plain in northeastern Taiwan located at the southern termination of the Okinawa Trough, which is formed by the back-arc extension of the Ryukyu subduction zone. Owing to this extensional tectonic setting, the Ilan Plain shows distributed hot springs with high geothermal gradient in several places, such as the Chingshui, Jiaoxi, Longde-Lize and Hongchailin areas. These are potential locations for geothermal exploration which require a thorough investigation to understand their geothermal system and to evaluate their potential in geothermal power generation. Seismic velocity provides key information to determine properties of a geothermal system including the distribution of fluids, fractures, and porosity. This study obtained seismic velocity images of the Ilan Plain and the surrounding area by joint inversion of body wave travel times of local earthquakes and Rayleigh wave phase velocities from ambient noise correlations recorded by a temporary dense geophone array in the Ilan Plain and the Formosa Array in northeastern Taiwan. The joint inversion takes advantage of the complementary sensitivities of both data types to better constrain both shallow and deep structures. In addition, we also lift the flat earth surface assumption commonly assumed in the surface wave tomography to avoid possible biased velocity structure due to topography by adapting the surface wave sensitivity kernel to the surface topography in the inversion. The obtained image at the 1-km depth shows low Vp and Vs corresponding to unconsolidated Quaternary sediments. The deeper images at 2- to 5-km depths show a low-velocity corridor extending from the Guishan volcanic island northeastern offshore to the southwest corner of the Ilan Plain, implying that the heat source of the geothermal systems in the Ilan Plain may be related to magmatic intrusions of backarc rifting. Locally, in the shallow region of the Chingshui and Jiaoxi area and the deeper region of the Hongchailin and Longde-Lize area, the high Vp/Vs ratio with little increase in Vp and significant decrease in Vs could indicate a saturated rock with high porosity, based on the rock physics principles in geothermal environment summarized in previous study. The low Vp, Vs, and Vp/Vs ratio in the shallow region of the Hongchailin area could indicate vapor-rich high temperature environment. Our results demonstrate the potential of new seismic imaging integrating body- and surface-wave data for geothermal exploration.

Data and slip inversion scripts for submitted paper: Interplay between seismic and aseismic deformation on the Central Range fault during the 2013 Mw 6.3 Ruisui earthquake (Taiwan) (in revision), This research is supported by the Ministry of Science and Technology (Taiwan) grant MOST 111-2116-M-001-018.

In observational seismology, the long-period background noise level in horizontal seismometer components is always higher than the vertical component at the same location. It is believed that the horizontal long-period noise is mostly attributed to ground tilt, yet the authentic tilt recordings of background noise in the seismic frequency band (0.01–20 Hz) have not been recorded successfully. We demonstrate the use of a newly developed optical-based rotation sensor, blueSeis-3A, to correct for the tilt effect in a horizontal seismometer. A station with a horizontal long-period (1 < T < 100 s) background noise level higher than the global new high-noise model was chosen, where a seismometer, a tiltmeter, and a rotation sensor were collocated. We first confirmed that the horizontal recordings from a tiltmeter and a seismometer were visually consistent, although it was unclear if tilt contamination existed in both recordings. It became evident until the ground tilt recorded by a rotation sensor was found to be waveform-matched with them, indicating that both sensors were contaminated by tilt. The spectrum of tilt records showed that ground tilts were mostly at period bands >1 s. By subtracting tilt from seismometer records, the horizontal background noise levels could be improved, approximately to the resolution level of the rotation sensors. Our results demonstrate that collocating rotation sensors with seismometers is a feasible way to improve the quality of the long-period background noise level in seismometer horizontal components when rotation sensors are sufficiently sensitive.

Taiwan is a hotbed of seismic and orogeny activity and this is the basis of the research of Dr Hsin-Hua Huang, Earth Structures Laboratory, Institute of Earth Sciences, Academia Sinica, Taiwan. He has illuminated detailed crustal and slab structures that have furthered understanding of Taiwan orogeny, incorporated ambient noise data to resolve high-resolution imaging of the volcanic and fault structure in northern Taiwan and conducted research that led to the discovery of multi-layering magma beneath the Yellowstone supervolcano in the US. The ultimate goal of his diverse studies is to achieve an improved imaging of the structure of the Earth and establish better understanding of the orogenic tectonic process and assess and mitigate natural hazards, such as volcanoes and earthquakes. In their latest project, Huang and the team are using the seismic wave interferometry method, combined with Taiwan's existing real-time signal transmission Taiwan Broadband Seismic Network (BATS) and the Central Weather Bureau Seismic Network (CWB24), to develop an automated real-time seismicity change detection system. The idea is that by measuring changes in the transmission velocity of seismic waves in the crust, physical parameters such as the degree of rock compression or changes in porosity can be linked and discussed. The researchers have performed an extensive review of knowledge about the current stage of fault zone failure and healing processes,the advantages of seismic noise interferometry and the need for Taiwan fault zone monitoring and related seismic interferometry research. In order to understand the temporal changes in crustal structure and the behaviour of velocity changes across faults, a long-term and stable real-time seismic velocity change monitoring system is necessary.

We constructed a 3-D coherent velocity model by extracting the common features from recent tomographic models and utilized the forward gravity modeling and wavelength filtering method to explore the depth origin of the gravity anomalies, such as the long-puzzling Puli Bouguer gravity low in west central Taiwan. The similarity analysis among the tomographic models shows the velocity structure most reliable in the depth range from 5 to 35 km. Using empirical velocity-to-density relationships, we show that the calculated Bouguer gravity anomalies from the 3-D coherent velocity model could well reproduce the gravity observations in general. Through filtering process, we separated the Bouguer gravity anomalies into shallow (0 - 17 km) and deep gravity effects (17 - 60 km) for structural exploration. The results show that the shallow gravity effect mainly reflects the surface geological features with low gravity values for unconsolidated sediments in plain and foothill areas to the west and high values for exhumed metamorphic rocks in the mountainous areas to the east. The deep gravity effect reveals the lowest gravity anomalies located in central Taiwan beneath the western Central Range. The Puli Bouguer gravity low is likely a coincident feature arising from the mismatch of the shallow and deep gravity effects due to the N-S trending undulation of crustal thickness beneath the western plain/foothill. This crustal thickness undulation may be related to the rifting activity of Taihsi and Tainan basins in the past. Better discriminating the gravity effect from shallow and deep crust could help better understand the architecture and tectonic process of the Taiwan orogenic belt.

1,4,5,8-Naphthalenediimides (NDIs) are widely used motifs to design multichromophoric architectures due to their ease of functionalisation, their high oxidative power and the stability of their radical anion. The NDI building block can be incorporated in supramolecular systems by either core or imide functionalization. We report on the charge-transfer dynamics of a series of electron donor–acceptor dyads consisting of a NDI chromophore with one or two donors linked at the axial, imide position. Photo-population of the core-centred π–π* state is followed by ultrafast electron transfer from the electron donor to the NDI. Due to a solvent dependent singlet–triplet equilibrium inherent to the NDI core, both singlet and triplet charge-separated states are populated. We demonstrate that long-lived charge separation in the triplet state can be achieved by controlling the mutual orientation of the donor–acceptor sub-units. By extending this study to a supramolecular NDI-based cage, we also show that the triplet charge-separation yield can be increased by tuning the environment., Ultrafast electron transfer from singlet and triplet excited states in equilibrium results in the population of both singlet and triplet charge-separated states.

Theoretical models and empirical works on the relationship between transaction-specific investments (TSIs) and firm performance have produced inconsistent results. Such results highlight a need for further investigation of long-debated questions concerning how TSIs enhance firm performance. In synthesizing transaction cost theory, a resource-based model, and relational exchange theory, this study presents a collective switching cost perspective and proposes the mediating role of supply chain integration (SCI) for reexamining TSI-performance relationships. A survey of 84 firms listed in the List of Taiwan Central Satellite Production Systems shows that TSIs positively affect firm performance and supply chain integration. Supply chain integration negatively affects firm performance relationships. This investigation confirms the mediating effect of SCI on the relationship between TSIs and firm performance.

Ce0.5Zr0.5O2 supported Ni-based catalysts with a Ni loading of 10 wt% and a B loading of 0.5 wt% were prepared by co-precipitation (assigned as NiCeZr(C) and BNiCeZr(C), respectively) and impregnation (assigned as NiCeZr(I) and BNiCeZr(I), respectively) procedures to evaluate the effects of fabrication methods and B-doped on the catalytic performance for steam reforming of ethanol (SRE). These catalysts were characterized with XRD, TPR, TPO, TEM, BET, TG and EA. The well dispersed active species that can be obtained through co-precipitation and formation of a Ni B alloy come from a B-doped catalyst, which can promote catalysis performance and reaction pathway. Further, it can improve the selectivity of hydrogen for a SRE reaction. Also, the B-doped catalysts possess a high oxygen storage capacity (OSC) via formation of CeBO3 under SRE ambience, which is the factor for removal of the carbonaceous species. TG and EA analyses demonstrate that there are fewer carbon deposits for the B-doped catalysts. The performance of the BNiCeZr(C) catalyst was preferential among these catalysts.

Ambient noise interferometry is a promising technique for studying crustal behaviors, providing continuous measurements of seismic velocity changes (dv/v) in relation to physical processes in the crust over time. In addition to the tectonic-driven dv/v changes, dv/v is also known to be affected by environmental factors through rainfall-induced pore-pressure changes, air pressure loading changes, thermoelastic effects, and so forth. In this study, benefiting from the long-term continuous data of Broadband Array in Taiwan for Seismology (BATS) that has been operated since 1994, we analyze continuous seismic data from 1998 to 2019 by applying single-station cross-component (SC) technique to investigate the temporal variations of crust on seismic velocity. We process the continuous waveforms of BATS stations, construct the empirical Green’s functions, and compute daily seismic velocity changes by the stretching technique in a frequency band of 0.1 to 0.9 Hz. We observe co-seismic velocity drops associated with the inland moderate earthquakes. Furthermore, clear seasonal cycles, with a period of near one-year, are also revealed at most stations, but with different characteristics. Systematic spectral and time-series analyses with the weather data are conducted and show that the rainfall-induced pore-pressure change is likely the main cause to the seasonal variations with high correlations. The strong site-dependency of these seasonal variations also precludes air pressure and temperature which varies smoothly in space from being dominant sources and suggests spatially-varying complex hydro-mechanical interaction across the orogenic belt in Taiwan.

Spatiotemporal evolution of earthquake clusters can give insights into fault geometry, triggering process, and potential interaction with fluid and heat. Taiwan is one of the most active orogenic belts with high deformation rate and complex crustal structures, so it is expected to observe seismicity driven by varying mechanisms among different geological processes. For investigating the tectonic complexity and the triggering processes of seismicity in Taiwan, a high-quality and robust catalog of earthquake clusters is critical. This study collected a long-term-effort earthquake catalog from the Central Weather Bureau from 1990/01 to 2018/06 and produced the earthquake cluster and background seismicity catalogs by four different declustering methods. Among which, the statistics-based nearest neighbor approach (NNA) performs most desirably for passing the Poisson process statistic tests while also remaining more events. We further classified the extracted earthquake clusters into the typical mainshock-aftershock (M-A) sequences and the swarms. Most of the M-A sequences are distributed near the Western Foothill. The asperity sizes, duration, and cluster event numbers all show positive correlations with mainshock magnitude. In contrast, the swarms are mainly distributed in the northern and southern Central Range and the northern Hualien regions. The lower correlation of the asperity sizes, duration, and swarm event numbers with the mainshock magnitude is showed in swarms. Moreover, we find that some of the swarm may be driven by fluid diffusion and spatial correlated with the high heat flow and spring regions.

Taiwan located at the convergence margin of the Eurasian Plate (EP) and Philippine Sea Plate (PSP) is one of the most active orogenic belts around the world. Under vigorously tectonic activities, the northern Taiwan is composed of complicated geological features including rifting basins, fold-and-thrust systems, volcanoes, and hydrothermal activity. In this study, we apply the technique of Ambient Noise Tomography (ANT) to eight months of continuous waveforms from the Formosa Array and Broadband Array for Seismology in Taiwan (BATS), with 137 broadband stations and ~5km station spacing. We first calculate multi-components cross-correlation functions to extract the information of Rayleigh wave signals. We then invoke Eikonal tomography to calculate the phase velocity map through 3 to 10 second periods and estimate Rayleigh wave ellipticity at each station between 2 to 13 second periods. For each grid point, we jointly invert the two types of Rayleigh wave measurements through a Bayesian-based inversion method to obtain the local 1-D shear wave velocity model. All 1-D models are then combined to construct a comprehensive 3-D model. Our 3-D model reveals upper crustal structures that well correlate with surface geological features. Near the surface, the model delineates the low-velocity Taipei and Ilan basins from the adjacent fast-velocity mountainous areas, with basin geometries consistent with the results of previous geophysical exploration and geological studies. At greater depths, low velocity anomalies are observed associated with the Linkou tableland, Tatun volcano group, and a possible dyke intrusion beneath the southern Ilan basin. The model also provides new geometrical constraints on the major active fault systems in the area, which are important to understand the basin formation and orogeny dynamics. The new 3-D shear wave velocity model allows a comprehensive investigation of shallow geologic structures in northern Taiwan.

The collision between the Eurasian and Indian plates since about 65 Ma caused extensive deformation in the Tibetan Plateau and surrounding areas. Northern Vietnam located in the southeastern Himalayan syntaxis is directly influenced by the collision and extrusion through the Red River shear zone that runs from southeastern Tibet to the South China Sea. Knowledge of crustal structure characteristics in northern Vietnam and across the Red River shear zone is crucial to improve our understanding not only of seismic hazards in the region but also of the regional Himalayan tectonic evolution as a whole. Seismic tomography is one of few methods that allows to study the subsurface structures effectively. In this study, we perform a joint tomographic inversion for northern Vietnam integrating the P- and S-direct waves traveling in the crust and the head waves along the Moho waves arrival time from more than 1000 earthquakes observed by Vietnamese networks. The obtained velocity model shows a good correlation with shallow geological features but also some complexity at crustal-scale. Several velocity anomalies bounded by and across the fault zones are revealed and discussed Keyword: Traveltime tomography, Northern Vietnam, VpVs ratio, crustal structure, Vietnam seismic network

A simultaneous combination of porosity and tunable optoelectronic properties, common in covalent organic frameworks, is rare in shape-persistent organic cages. Yet, organic cages offer important molecular advantages such as solubility and modularity. Herein, we report the synthesis of a series of chiral imine organic cages with three built-in rylene units by means of dynamic imine chemistry and we investigate their textural and optoelectronic properties. Thereby we demonstrate that the synthesized rylene cages can be reversibly reduced at accessible potentials, absorb from UV up to green light, are porous, and preferentially adsorb CO2 over N2 and CH4 with a good selectivity. In addition, we discovered that the cage incorporating three perylene-3,4:9,10-bis(dicarboximide) units displays an efficient delayed fluorescence. Time-correlated single photon counting and transient absorption spectroscopy measurements suggest that the delayed fluorescence is likely a consequence of a reversible intracage charge-separation event. Rylene cages thus offer a promising platform that allows combining the porosity of processable materials and photochemical phenomena useful in diverse applications such as photocatalysis or energy storage., Chiral rylene imine cages combine porosity and tunable optoelectronic properties. They adsorb CO2 over N2 with good selectivity and can show an efficient delayed fluorescence.

A simultaneous combination of porosity and tunable optoelectronic properties, common in covalent organic frameworks, are rare in shape-persistent organic cages. Yet, organic cages offer important molecular advantages, the solubility and modularity. Herein, we report the synthesis of a series of chiral imine organic cages with three built-in rylene units by means of dynamic imine chemistry and we investigate their textural and optoelectronic properties. Thereby we demonstrate that the synthesized rylene cages are porous, can be reversibly reduced at accessible potentials, and can absorb from UV up to green light. We also show that they preferentially adsorb CO2 over N2 and CH4 with a good selectivity. In addition, we discovered that the cage incorporating three perylene-3,4:9,10-bis(dicarboximide) units displays a delayed fluorescence, likely as a consequence of formation of a correlated triplet pair, the multiexciton state in singlet fission. Rylene cages thus represent a unique platform to investigate the effect of electronic properties on material porosity and, at the same time, to probe excited-state phenomena in the limit of vanishing interchromophore coupling.

A sequence of eruptions in the lower East Rift Zone (LERZ) of the Kilauea, Hawaii volcano commenced in early May 2018 and caused serious damage and residential evacuation. The post-eruption drainage and collapses of the summit lava lake and caldera suggest a well-connected magmatic plumbing system along the rift zone. How and when the pre-eruptive magmatic processes in such connecting system occurred are, however, still unclear. For that, we apply ambient noise interferometry with seismic data from January 2017 to June 2018 from 12 broadband seismometers to investigate spatiotemporal seismic velocity changes (dv/v) of the upper crust in the Kilauea area. The dv/v variations in three frequency bands (0.3–0.6 Hz, 0.6–0.9 Hz, and 0.9–2.0 Hz) show distinct responses to strong earthquake ground shaking and deep magmatic intrusion processes. Earthquake-induced dv/v drops mainly in the higher two frequency bands imply shallow mechanical changes within the uppermost 1 km of the crust. In contrast, the magma-related dv/v changes can be characterized into three periods of activity: from the December 2017 to March 15, 2018, a dv/v excursion only seen in the lowest frequency band indicates the magmatic intrusion processes taking place at the depth range of 1–4 km, consistent with the proposed depth of the magma reservoir-dike system in the rift zone. The spatial dv/v distribution suggests that the magma may intrude to the deeper summit magma reservoir and in the upper East Rift Zone (UERZ) at this time. From March 15 to April 17 in 2018, the summit inflation recorded by tiltmeters causes the dv/v increases in the higher two frequency bands. After April 17 to the eruption, the accumulating damage of the edifice together with the stronger intrusion activity in the UERZ result in dv/v decreases in all three frequency bands around the summit and UERZ areas. Our observations highlight that the ambient noise interferometry analysis provides an opportunity to image and understand the pre-eruptive processes of reservoir-dike magma system and could be a useful supplement to current volcanic monitoring systems.

Key Points: • A pronounced low velocity anomaly (>15%) beneath the Tatun volcano group is found at the depths of 5-25 km as the magma reservoir. • A high melt fraction of ~16% for the magma reservo...

In this study, we have mapped for the first time robustly the 3D structure of two upper-crustal magmatic reservoirs beneath the active volcanoes Avacha and Koryaksky, which are called “home volcanoes” for Petropavlovsk-Kamchatsky, the main city of Kamchatka (~200,000 inhabitants). These volcanoes represent a serious potential hazard for the city, because they are located at a distance of 25–30 km from the populated areas. A new tomographic model (VP, VS, VP/VS ratio) was built, for which we used the arrival times of seismic P- and S-waves from almost 5,000 local events, recorded by a permanent network of seismic stations during 2009–2018.The resolution of the derived models was carefully tested by a series of synthetic simulations. Prominent anomalies with extremely high VP/VS ratios (up to 2.4) were retrieved directly beneath both volcanoes and interpreted as magma reservoirs containing high degrees of partial melt and/or fluids. Beneath Avacha, the upper limit of the anomaly is located at the depth of ~2 km below the surface. The reservoir appears to be connected to the surface by a neck-shaped anomaly of high VP/VS ratio associated with active seismicity, which is interpreted as a magma and fluid conduit. Beneath Koryaksky, the magma related anomaly is deeper: its upper limit is located at a depth of ~ 7 km below the surface. This anomaly is connected with the volcanic coneby a vertical seismicity cluster, which possibly marks the pathway of fluid ascent and degassing. Between the volcanoes, a 2–3 km thick layer of very low VP and VS is interpreted as deposits of volcanoclastic sediments. Generally low Vp/Vs ratios in the area between the volcanoes show that the magma reservoirs in the upper crust are not interconnected.This study was partially supported by the RFBR project # 18-55-52003.

The fold-thrust belt of southern Taiwan currently accommodates rapid westward shortening in the order of 4.5 mm/a and is estimated to have developed since the Late Pliocene. It is the locus of the 2016 Mw6.4 Meinong earthquake, which involved fault slip at multiple levels in the mid-to-upper crust. It nucleated at ~15 km depth and also triggered shallow structures that reach the surface or nearly. To characterize the structure of the piedmont and investigate the broader tectonic setting of the event, we build two east-west regional balanced cross-sections based on surface geology, subsurface data, coseismic and interseismic geodetic data, and published nanno- and magneto-stratigraphy. We also document the first-order evolution of the piedmont and how the piedmont structures relate to the inner part of the mountain belt based on the cross-section restoration and the analysis of the seismic velocity structure of the plate boundary.From the Coastal Plain towards the east, we propose a series of three active west-dipping backthrusts, rooted on a ~4.0-km-deep detachment, the Tainan detachment. The detachment lies within the base of the 3-km-thick Plio-Pleistocene Gutingkeng mudstone, which represents the initial foreland basin sediments. Syntectonic sediments and rapid shortening and uplift observed from geodetic measurements attest for the activity of these structures since the Late Pleistocene. Further east, the Tainan detachment ramps down to ~7 km depth, allowing the east-dipping Lungchuan and Pingchi thrusts to bring Upper Miocene continental-shelf formations to the surface. The cross-section restoration indicates less than 10 km shortening since ~450 ka or less on the Tainan detachment and the frontal backthrusts, while the east-dipping Lungchuan and Pingchi thrusts each consumed ~10 km shortening. Another ramp from ~7 to ~11 km depth is expected further east based on older sediments and slates exposed on the hanging wall of faults in the inner part of the mountain belt. This ~11-km-depth detachment seems to correspond with an inversion in seismic velocities at ~12 km depth beneath the slates belt, interpreted as slates over-riding lower-velocity passive margin sediments. Therefore, the detachment and thrusts system proposed from our cross-section appears to correspond to the main plate interface, where significant shortening was consumed in a thin-skinned deformation style, involving only foreland basin sediments near the deformation front.The Meinong earthquake coseismic surface deformation suggests that, in addition to the deepest (15-20 km) main fault plane, the ~4-7-km-depth ramp, the Tainan detachment and the backthrusts slipped aseismically during after the earthquake. In contrast, the earthquake nucleated below the main detachment and, based on tomographic models, there is no clear structural connection between deep and shallower structures. The Meinong event locates near the interface between Cenozoic basement rocks and post-rifting sediments, similarly to the 2010 Mw6.3 Jiashian event. We propose that this interface is the locus of moderate-magnitude events, which seismic waves triggered limited slip on shallower faults, rooted within the weak, fluid-rich Gutingkeng mudstone. This interface may have developed as a secondary detachment level with limited total shortening.

It is always tricky to definite deep-seated or massive scale landslide investigation and monitoring. The scars could map from a high-resolution digital elevation model. However, the activity or sliding depth is merely difficult to define before installing a monitoring system. Lantai potential landslide area is selected for testing and demonstrating newly developed scientific investigation and monitoring techniques. Possible landslide scars have mapped from airborne lidar data, which provided a reference area for DInSAR analysis. More than ten years of DInSAR analysis shows an active/fast-moving area. The sliding plane and geological structure defined from customized earthquake stations and UAV LiDAR following with field verification. The background noise detection can define potential sliding planes from various precipitation events or earthquakes. GPS/leveling stations are installed to monitor ground deformation and verification from DInSAR results providing single point information to the whole area. The drilling holes’ depth is determined from earthquake stations analysis result, geological data, and sliding model from preliminary numerical analysis. Resistivity poles are installed at two holes from 100m beneath the ground surface with connected poles between these two holes to form a window shape monitoring system. The window shape Resistivity Image Profiling system can measure continuously providing not only geological structure variance and groundwater passing this window. New developed optical-fiber water pressure gauges are installed at different depths to verified groundwater pressure and water flow. The deformation system including extensometer, MEMS inclinometer, In-Plane Inclinometer, and Shape Acceleration Array are installed to provide direct displacements from the ground surface to underground. The sliding threshold is thus defined with various measurements from different monitoring methods and with different scales.

We analyze teleseismic P-to-S conversions for high-resolution imaging of the mantle transition zone beneath the Colorado Rocky Mountains using data from a dense PASSCAL seismic broadband deployment. A total of 6,021 P-to-S converted receiver functions are constructed using a multi-channel minimum-phase deconvolution method and migrated using the common converted point technique with the 3-D teleseismic P- and S-wave tomography models of Schmandt and Humphreys (2010) . The image finds that the average depths of the 410-km discontinuity (the 410) and 660-km discontinuity (the 660) at 408 ± 1.9 km and 649 ± 1.6 km respectively. The peak-to-peak topography of both discontinuities is 33 km and 27 km respectively. Additionally, prominent negative polarity phases are imaged both above and below the 410. To quantify the mean properties of the low-velocity layers about 410 km, we utilize double gradient layer models parameterization to fit the mean receiver function waveform. This waveform fitting is accomplished as a grid-search using anelastic synthetic seismograms. The best-fitting model reveals that the olivine–wadsleyite phase transformation width is 21 km, which is significantly larger than anhydrous mineral physics prediction (4–10 km) ( Smyth and Frost, 2002 ). The findings of a wide olivine–wadsleyite phase transformation and the negative polarity phases above and below the 410, suggest that the mantle, at least in the 350–450 km depth range, is significantly hydrated. Furthermore, a conspicuous negative polarity phase below the 660 is imaged in high velocity region, we speculate the low velocity layer is due to dehydration flux melting in an area of convective downwelling. Our interpretation of these results, in tandem with the tomographic image of a Farallon slab segment at 800 km beneath the region ( Schmandt and Humphreys, 2010 ), is that hydrous and upwelling mantle contributes to the high-standing Colorado Rocky Mountains.

Earthquake-triggered landslides are one of the major hazards in tectonically active mountain belts, and a nowcasting (near-real-time assessment) model for rapid assessment of coseismic landsliding is crucial for hazard mitigation and management. The purpose of this study is to develop a nowcasting model by using a logistic regression model. We use an inventory of earthquake-triggered landslides from the 1999 Mw7.6 Chi-Chi earthquake to train the model at a spatial resolution of 40 m. We use a multi-stage framework to choose dominant variables for developing an optimal model. Our result shows that the model contains three key variables, peak ground acceleration (PGA), topographic roughness, and lithology, and two essential combined variables, PGA*slope, and PGA*roughness, to enhance the interaction between ground shaking and topography. By using the landslide inventory of the 1998 Mw5.7 Jueili earthquake, the probability threshold of 0.1 is chosen to define predicted landslides, and the balanced accuracy is above 0.95 in the prediction. The development of this model can effectively estimate possible earthquake-triggered landslides with the input of real-time PGA values, and facilitate a rapid response in emergencies based on the potential landslide distributions in Taiwan.

The inner core (IC) east–west hemispheric dichotomy is widely recognized, but the reported position of the hemispheric boundary varies among studies due to uneven sampling coverage and the data analyzed. This study investigates the sharpness of the western hemispheric boundary (WHB) near 180 °W by analyzing differential time residuals of PKiKP–PKPdf and PKP(bc–df) for PKPdf phases that sample 155 °E–130 °W in various azimuthal directions. Using PKiKP–PKPdf observations, the WHB is located at 175 °E–180 °W in the southern hemisphere, based mainly on the lateral isotropy–anisotropy transition. However, based on the lateral isotropic velocity contrast and this isotropy–anisotropy transition between the two hemispheres, its location is 170–160 °W in the northern hemisphere. These findings indicate that the WHB is sharp and exhibits a latitudinal dependence with a 10°–20° kink, as well as 1.75% anisotropy in the uppermost IC across the 180–155 °W range of the western hemisphere. As suggested by PKP(bc–df), the WHB could remain at 160 °W at depth. The isotropic velocity contrast near the WHB (160 °W) between the eastern and western hemispheres is lower than previous estimates using PKPdf phases sampling the bulk part of each hemisphere.

Despite a moderate magnitude, M_w = 6.4, the 5 February 2016 Meinong, Taiwan, earthquake caused significant damage in Tainan City and the surrounding areas. Several seismograms display an impulsive S-wave velocity pulse with an amplitude of about 1 m s-1, which is similar to large S-wave pulses recorded for the past several larger damaging earthquakes, such as the 1995 Kobe, Japan, earthquake (M_w = 6.9) and the 1994 Northridge, California, earthquake (M_w = 6.7). The observed PGV in the Tainan area is about 10 times larger than the median PGV of M_w = 6.4 crustal earthquakes in Taiwan. We investigate the cause of the localized strong ground motions. The peak-to-peak ground-motion displacement at the basin sites near Tainan is about 35 times larger than that at a mountain site with a similar epicentral distance. At some frequency bands (0.9 - 1.1 Hz), the amplitude ratio is as large as 200. Using the focal mechanism of this earthquake, typical “soft” and “hard” crustal structures, and directivity inferred from the observed waveforms and the slip distribution, we show that the combined effect yields an amplitude ratio of 17 to 34. The larger amplitude ratios at higher frequency bands can be probably due to the effects of complex 3-D basin structures. The result indicates that even from a moderate event, if these effects simultaneously work together toward amplifying ground motions, the extremely large ground motions as observed in Tainan can occur. Such occurrences should be taken into consideration in hazard mitigation measures in the place with frequent moderate earthquakes.

Rapid shortening in convergent mountain belts is often accommodated by slip on faults at multiple levels in upper crust, but no geodetic observation of slip at multiple levels within hours of a moderate earthquake has been shown before. Here we show clear evidence of fault slip within a shallower thrust at 5–10 km depth in SW Taiwan triggered by the 2016 Mw 6.4 MeiNong earthquake at 15–20 km depth. We constrain the primary coseismic fault slip with kinematic modeling of seismic and geodetic measurements and constrain the triggered slip and fault geometry using synthetic aperture radar interferometry. The shallower thrust coincides with a proposed duplex located in a region of high fluid pressure and high interseismic uplift rate, and may be sensitive to stress perturbations. Our results imply that under tectonic conditions such as high-background stress level and high fluid pressure, a moderate lower crustal earthquake can trigger faults at shallower depth.

International audience; Ice-covered ocean worlds possess diverse energy sources and associated mechanisms that are capable of driving significant seismic activity, but to date no measurements of their seismic activity have been obtained. Such investigations could reveal the transport properties and radial structures, with possibilities for locating and characterizing trapped liquids that may host life and yielding critical constraints on redox fluxes and thus on habitability. Modeling efforts have examined seismic sources from tectonic fracturing and impacts. Here, we describe other possible seismic sources, their associations with science questions constraining habitability, and the feasibility of implementing such investigations. We argue, by analogy with the Moon, that detectable seismic activity should occur frequently on tidally flexed ocean worlds. Their ices fracture more easily than rocks and dissipate more tidal energy than the