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To improve the grinding accuracy of roller enveloping hourglass worm tooth surface, a novel precision processing method with precision modification is proposed based on the kinematic inversion. The mathematical model of worm drive tooth surface is established, and the modification principle of tooth surface is revealed with non-backlash meshing. The processing method of tooth surface is proposed based on the kinematic inversion principle, and the modification principle of roller hourglass worm are discussed. The tooth surface fundamental errors of grinding hourglass worm are analysed based on the wear of the finger-like grinding wheel, and the maximum wear amount of finger-like grinding wheel radius is presented. An hourglass worm grinder integrating tooth surface machining and modification is developed, and the sample cutting and accuracy detection were carried out. The comprehensive processing errors of this hourglass worm sample is 14.3 μm, and transmission error of worm drive prototype is 41.6 arcsecond, while the lost motion is 14.4 arcsecond. The results show that this novel grinding method can ensure the precision transmission of roller enveloping hourglass worm drive. [ABSTRACT FROM AUTHOR]

We determined the main parameters of the source rupture process of intermediate- and deep-depth earthquakes occurring in the Peru–Brazil–Bolivia border region and northern Chile. The parameters of depth, fault-plane orientation, scalar seismic moment, slip distribution, and radiated seismic energy are obtained from seismograms. We selected 15 intermediate-depth earthquakes (100 km < h < 300 km) and 10 very deep earthquakes (h > 500 km) with magnitudes MW ≥ 6.0. For most events, the slip distribution over the rupture plane shows a single asperity, and the source time function presents a simple pulse. There are differences between intermediate-depth and deep earthquakes. The rupture areas, maximum slip and source time function (STF) duration are larger for intermediate-depth events than for deep events. Additionally, the STF's show a sharper increase for deep earthquakes. The scaled radiated seismic energy shows larger values for deep depth events. The stress regime pattern derived from the obtained focal mechanism agrees with the geometry of the subduction of the Nazca plate. At intermediate depths, in the northern area up to 12°S, the stress pattern corresponds to a horizontal extension, while in the southern area, the tension axes dip at an angle of 30°. At deep depths, the stress regime corresponds to vertical compression in the north and dips of approximately 45° in the south. [ABSTRACT FROM AUTHOR]

We use Sentinel‐1 Interferometric Synthetic Aperture Radar observations to derive the first complete map of slip‐rate distribution at km‐scale along the 1,000‐km‐long Haiyuan fault system, and further to analyze its earthquake potential. Rate distribution reveals four highly locked asperities (slip rate <1 mm/yr) and three creeping regions (slip rate ranges from 2 to 5 mm/yr) at depths of 0–20 km. Based on the rate distribution, we estimate seismic moment accumulation rate, and by combining historical earthquake records, we calculate the moment deficits on each fault segment. Results show that many fault segments have accumulated a seismic moment that equates to an Mw > 7.0 earthquake. The westernmost fault segment has been rarely mentioned in previous studies, but our calculations show evidently that it is capable of producing Mw > 7.0 earthquakes given the high seismic moment accumulation rate and a lack of small‐to‐moderate earthquakes. Plain Language Summary: Faults accumulate strains over long periods of seismic quiescence between great earthquakes, that is, interseismic strain accumulation, and release them either seismically by producing earthquakes or aseismically as creep. Studies of such strain accumulation and release processes are critical for understanding regional seismic hazard. We focus here on the 1,000‐km‐long Haiyuan fault system in northeastern Tibet. By using the most recent geodetic data sets, we quantify strain accumulation along the fault and evaluate its seismic potential. We derive fault slip rate distribution and calculate along‐strike seismic moment accumulation rate. Combining our knowledge of previous earthquake ruptures, including the time, extent and size, we compute the total seismic moment that has accumulated on each fault segment since the last major event. We find high seismic potentials along many fault segments, such as Lenglongling, Jinqianghe‐Maomaoshan and Gulang, which can generate an Mw > 7.0 earthquake anytime from now. Toward the western end, earthquake history remains poorly understood, but our analysis shows that the westernmost segment can produce Mw > 7.0 earthquakes, which deserves more attention. Key Points: Slip‐rate distribution at kilometer scale along the 1,000‐km‐long Haiyuan fault system is derived from high‐resolution Interferometric Synthetic Aperture Radar dataFine‐scale rate distribution reveals four highly locked asperities and three creeping regions at depths of 0–20 kmAlong‐strike seismic moment accumulation rate and deficits are computed based on rate distribution and earthquake rupture history [ABSTRACT FROM AUTHOR]

Abstract The boundary between the Northern Andean block and the South American plate is a first‐order tectonic structure in Colombia with historically M > 7 earthquakes. However, details about individual sections of the system remain unknown. We illuminate the seismotectonic of the Algeciras fault by investigating an earthquake sequence that started on 24 December 2019. Using seismic networks at region, we estimate foreshocks and aftershocks focal mechanisms, local stress field, kinematic slip models of the largest events, and Coulomb stress changes. We integrate seismological and morphostructural observations to characterize source properties and reinterpret local faults. Two mainshocks (doublet of Mw 6.0 and 5.8) occurred within 16 min, rupturing just a few kilometers from each other. Discrimination of causative faults among the centroid moment‐tensor nodal planes is difficult because the focal zone is a complex tectonic environment. The focal mechanisms and the local stress field obtained are consistent with a regional NE trending dextral transpressive shear. The relocated aftershocks show a cluster with an L‐shaped pattern concentrated in a ∼7 × 7 km area. Our model defines the Algeciras fault with two structural styles for its northern termination. The NW part is characterized by a duplex‐style of right‐lateral strike‐slip with inner secondary faults of the same sense of movement, and the SE zone by a domino‐style system with inner minor faults of sinistral kinematics. The earthquake doublet is in the zone characterized by the duplex style. In contrast, the southern part of the aftershocks is located in the zone characterized by the domino style.

We model the two most recent Mw~6 Parkfield, California, earthquakes, which occurred in 1966 and 2004, from a nonlinear global inversion of near-fault strong motion seismograms. Our rupture models are characterized by spatially variable slip amplitude and rake, rupture velocity, and risetime. The rupture models indicate that the two earthquakes generated slip in regions of the fault that are not identical, as earlier suggested. Given the sparse seismic data set available for the 1966 earthquake, we conduct a series of tests to verify our results: (1) we perform synthetic tests in order to study the resolution of the 1966 seismic data set; (2) we perform an inversion of the 2004 earthquake using a data set equivalent to the 1966 earthquake; and (3) we model the 1966 data set under the a priori assumption that it was similar to the 2004 earthquake. All of the tests, as well as independent observations, indicate that slip during the 1966 and 2004 Parkfield earthquakes occurred in different regions of the fault. This result implies that regions of a fault that are frictionally locked may remain locked even during a main shock (moderate-size earthquake). In this scenario, large earthquakes occur when all the locked regions of a fault are “synchronized” and ready to slip at the same time.

Abstract In this study, we estimated source process of the 2016 Kumamoto earthquake from strong-motion data by using the multiple-time window linear kinematic waveform inversion method to discuss generation of strong motions and to explain crustal deformation pattern with a seismic source inversion model. A four-segment fault model was assumed based on the aftershock distribution, active fault traces, and interferometric synthetic aperture radar data. Three western segments were set to be northwest-dipping planes, and the most eastern segment under the Aso caldera was examined to be a southeast-dipping plane. The velocity structure models used in this study were estimated by using waveform modeling of moderate earthquakes that occurred in the source region. We applied a two-step approach of the inversions of 20 strong-motion datasets observed by K-NET and KiK-net by using band-pass-filtered strong-motion data at 0.05–0.5 Hz and then at 0.05–1.0 Hz. The rupture area of the fault plane was determined by applying the criterion of Somerville et al. (Seismol Res Lett 70:59–80, 1999) to the inverted slip distribution. From the first-step inversion, the fault length was trimmed from 52 to 44 km, whereas the fault width was kept at 18 km. The trimmed rupture area was not changed in the second-step inversion. The source model obtained from the two-step approach indicated 4.7 × 1019 Nm of the total moment release and 1.8 m average slip of the entire fault with a rupture area of 792 km2. Large slip areas were estimated in the seismogenic zone and in the shallow part corresponding to the surface rupture that occurred during the Mj7.3 mainshock. The areas of the high peak moment rate correlated roughly with those of large slip; however, the moment rate functions near the Earth surface have low peak, bell shape, and long duration. These subfaults with long-duration moment release are expected to cause weak short-period ground motions. We confirmed that the southeast dipping of the most eastern segment is more plausible rather than northwest-dipping from the observed subsidence around the central cones of the Aso volcano. Graphical Abstract .

Abstract We study the rupture processes of Iquique earthquake M w 8.1 (2014/04/01) and its largest aftershock M w 7.7 (2014/04/03) that ruptured the North Chile subduction zone. High-rate Global Positioning System (GPS) recordings and strong motion data are used to reconstruct the evolution of the slip amplitude, rise time and rupture time of both earthquakes. A two-step inversion scheme is assumed, by first building prior models for both earthquakes from the inversion of the estimated static displacements and then, kinematic inversions in the frequency domain are carried out taken into account this prior information. The preferred model for the mainshock exhibits a seismic moment of 1.73 × 1021 Nm (M w 8.1) and maximum slip of ∼9 m, while the aftershock model has a seismic moment of 3.88 × 1020 (M w 7.7) and a maximum slip of ∼3 m. For both earthquakes, the final slip distributions show two asperities (a shallow one and a deep one) separated by an area with significant slip deficit. This suggests a segmentation along-dip which might be related to a change of the dipping angle of the subducting slab inferred from gravimetric data. Along-strike, the areas where the seismic ruptures stopped seem to be well correlated with geological features observed from geophysical information (high-resolution bathymetry, gravimetry and coupling maps) that are representative of the long-term segmentation of the subduction margin. Considering the spatially limited portions that were broken by these two earthquakes, our results support the idea that the seismic gap is not filled yet. Highlights • Causes of along-strike and -dip segmentations are revealed by Iquique earthquake. • This study shows that the Northern Chile seismic gap is not fully filled yet. • A multigrid two-step kinematic study is performed to avoid possible local minima. • Kinematic models are constrained by prior models built from static inversions. [ABSTRACT FROM AUTHOR]

By adopting the principle of kinematic inversion and the mathematical tools such as rotation matrix,the general analytic formula of cam contour of flat evolution type of high-speed printing press mechanism from German is obtained through deduction. The study and discussion surrounding the different values of the angle σ between flat and connecting rod are carried out,the problem of cam contour design of flat evolution type mechanism of is solved successfully,the important theoretical basis for further popularization and application of this evolution type is provided.

Abstract: The goal of hydraulic stimulation is to increase formation permeability in the near vicinity of a well. However, there remain technical challenges around measuring the outcome of this operation. During two enhanced geothermal system stimulations in South Australia, Paralana in 2011 and Habanero in 2003, extensive catalogs of microseismicity were recovered. It is often assumed that shear failure of existing fractures is the main mechanism behind both the induced earthquakes and any permeability enhancement. This underpins a common notion that the seismically active volume is also the stimulated reservoir. Here we compute the density of earthquake hypocenters and provide evidence that, under certain conditions, this spatiotemporal quantity is a reasonable proxy for pore pressure increase. We then apply an inverse modeling approach that uses the earthquake observations and a modified reservoir simulator to estimate the parameters of a permeability evolution relation. The regime implied by the data indicates that most permeability enhancement occurred very near to the wellbore and was not coincident with the bulk of the seismicity, whose volume was about 2 orders of magnitude larger. Thus, we conclude that, in some cases, it is possible for permeability enhancement and induced seismicity to be decoupled, in which case the seismically active volume is a poor indicator of the stimulated reservoir. Our results raise serious questions about the effectiveness of hydroshearing as a stimulation mechanism in enhanced geothermal system. This study extends our understanding of the complex processes linking earthquakes, fluid pressure, and permeability in both natural and engineered settings. [ABSTRACT FROM AUTHOR]

On 18 January 2017, the 2016−2017 central Italy seismic sequence reached the Campotosto area with four events with magnitude larger than 5 in three hours (major event MW 5.5). To study the slip behavior on the causative fault/faults we followed two different methodologies: (1) we use Interferometric Synthetic Aperture Radar (InSAR) interferograms (Sentinel-1 satellites) and Global Positioning System (GPS) coseismic displacements to constrain the fault geometry and the cumulative slip distribution; (2) we invert near-source strong-motion, high-sampling-rate GPS waveforms, and high-rate GPS-derived static offsets to retrieve the rupture history of the two largest events. The geodetic inversion shows that the earthquake sequence occurred along the southern segment of the SW-dipping Mts. Laga normal fault system with an average slip of about 40 cm and an estimated cumulative geodetic moment of 9.29 × 1017 Nm (equivalent to a MW~6). This latter estimate is larger than the cumulative seismic moment of all the events, with MW > 4 which occurred in the corresponding time interval, suggesting that a fraction (~35%) of the overall deformation imaged by InSAR and GPS may have been released aseismically. Geodetic and seismological data agree with the geological information pointing out the Campotosto fault segment as the causative structure of the main shocks. The position of the hypocenters supports the evidence of an up-dip and northwestward rupture directivity during the major shocks of the sequence for both static and kinematic inferred slip models. The activated two main slip patches are characterized by rise time and peak slip velocity in the ranges 0.7−1.1 s and 2.3−3.2 km/s, respectively, and by ~35−50 cm of slip mainly concentrated in the shallower northern part of causative fault. Our results show that shallow slip (depth < 5 km) is required by the geodetic and seismological observations and that the inferred slip distribution is complementary with respect to the previous April 2009 seismic sequence affecting the southern half of the Campotosto fault. The recent moderate strain-release episodes (multiple M~5−5.5 earthquakes) and the paleoseismological evidence of surface-rupturing events (M~6.5) suggests therefore a heterogeneous behavior of the Campotosto fault.

The 2016 Kaikōura (New Zealand) earthquake generated large ground motions and resulted in multiple onshore and offshore fault ruptures, a profusion of triggered landslides, and a regional tsunami. Here we examine the rupture evolution using two kinematic modeling techniques based on analysis of local strong-motion and high-rate GPS data. Our kinematic models capture a complex pattern of slowly ( Vr < 2 km/s) propagating rupture from south to north, with over half of the moment release occurring in the northern source region, mostly on the Kekerengu fault, 60 s after the origin time. Both models indicate rupture reactivation on the Kekerengu fault with the time separation of ~11 s between the start of the original failure and start of the subsequent one. We further conclude that most near-source waveforms can be explained by slip on the crustal faults, with little (<8%) or no contribution from the subduction interface. [ABSTRACT FROM AUTHOR]

On 24 November 2015 two events of magnitude Mw 7.5 and Mw 7.6 occurred at 600 km depth under the Peru–Brazil boundary. These two events were separated in time by 300 s. Deep event doublets occur often under South America. The characteristics that control these events and the dynamic interaction between them are an unresolved problem. We used teleseismic and regional data, situated above the doublet, to perform source inversion in order to characterize their ruptures. The overall resemblance between these two events suggests that they share similar rupture process. They are not identical but occur on the same fault surface dipping westward. Using a P-wave stripping and stretching method we determine rupture speed of 2.25 km/s. From regional body wave inversion we find that stress drop is similar for both events, they differ by a factor of two. The similarity in geometry, rupture velocity, stress drop and radiated energy, suggests that these two events looked like simple elliptical ruptures that propagated like classical sub-shear brittle cracks. [ABSTRACT FROM AUTHOR]

The kinematic rupture process of the 2011 M 9.0 Tohoku earthquake is inverted with an elliptical-patches method, using a genetic algorithm, for the purpose of rapid and robust estimation of the source parameters of a mega-earthquake. We use the ground-displacement field provided by a continuous GPS network and the ground-velocity field recorded by acceleration networks. In addition to the typical inversion procedure in which a data duration long enough to cover the whole rupture process is used, inversions based on shorter signals, giving an incomplete view over the ground shaking sequence, are also carried out. How fast can a robust estimation of the source parameters be obtained? Using the elliptical approximation, we find that robust solutions of M ~ 9.0-earthquakes are rather quickly obtained regardless of the frequency band and the elliptical patch description. It is also confirmed that, because of the absence of off-shore recording stations on the east side of the fault, some uncertainties in the rupture process cannot be completely removed. In fact, at the very low frequencies considered, the western part of the fault (deeper portion) contributes more significantly to the recorded signals than does the other end close to the trench. This problem also prevents refinement of the description of the rupture process, in particular when using more than one ellipse. [ABSTRACT FROM AUTHOR]

Abstract: The objective of the present work was the conjoint analysis of the efficiency and transmission ratio ranges that can be achieved with all the possible constructive solutions of four-, five-, and six-link planetary gear trains. We started from the graphs of these trains to determine all the structurally distinct kinematic inversions. We then obtained all the constructive solutions resulting from every possible combination of gear type and configuration. The result was thus the set of structurally and constructively different planetary gear trains. Next, we obtained the range of transmission ratio that can be achieved with each train, and the efficiency as a function of the transmission ratios within that range. This analysis revealed which trains allow both high transmission ratios and high efficiency, and are thus potentially most useful in the design of power transmission applications. They included a series of high efficiency trains whose potential utility had not as yet been investigated. Additionally, the study led to some interesting conclusions about the relationship between efficiency and transmission ratio in six-link planetary gear trains. [Copyright &y& Elsevier]

The Mw 7.0 Constitución earthquake of March 2012 is one of the largest interplate aftershocks of the Maule 2010 Mw 8.8 mega-thrust earthquake. This event was recorded by high-rate GPS stations, local seismometers and accelerometers, the Global Seismographic Network and SAR acquisitions by the ENVISAT satellite. We have used these data to perform a kinematic inversion and back projection to identify the principal characteristics of this event. The Constitución earthquake nucleated at 39 km depth and then propagated up-dip at subshear speed towards its centroid, with an unusually long initiation phase that lasted almost 6 s. The largest slip of this event was located in the deeper part of the subduction interface, between the region of maximum co-seismic slip of the 2010 Maule earthquake, and the area where rapid afterslip occurred following that event. Features of the Constitución earthquake may suggest that larger interplate aftershocks of the Maule event preferentially occur in the deeper part of the plate interface where ruptures are complex, produce high frequencies and involve numerous asperities. [ABSTRACT FROM AUTHOR]

Volcanic activity focuses along plate boundaries. However, large volcanoes are also found in intraplate settings. For these volcanoes, geodynamic processes responsible for magma generation and structural controls on magma rise and extrusion need to be evaluated. We merge original (field and remote sensing) and available (geodetic, geophysical, and petrological) data to consider the tectono-magmatic relationships of three large intraplate volcanoes in the E-Anatolian-Iranian plateau; Sar'akhor (NE Iran), Damavand (Central Alborz) and Ararat (E Anatolia). In NE Iran, a Miocene-Pliocene NW-trending compression activated E-W dextral faults to the NW of Sar'akhor and N-S sinistral faults to the SE, creating an extruding wedge to the west of this volcano. Since Quaternary, NE-trending compression inverted fault movement, hindering further block extrusion and volcanism terminated. The adakitic composition of the Sar'akhor rocks suggests post-collisional melting of oceanic slab and/or mafic lower crust, possibly triggered by an asthenospheric rise after slab break-off or intramantle delamination. For the active Damavand and Ararat volcanoes, available data suggest magma generation due to rising hot asthenosphere, following lithospheric delamination or slab break-off in a transtensional environment. The features common to Sar'akhor, Damavand and Ararat allow proposing a model, where transtension focuses the rise of magma in intraplate settings overlying hot asthenosphere produced by delamination or slab break-off. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes the theoretical aspects that aimed the realization of an anthropometric robotic leg. It contains a brief overview of the mechanical structure and an accurate description of the prototype kinematical behavior. In particular, two different numerical methods for solving the kinematical inversion process are described in details. Moreover, the aim of this project is the development of new technologies for the realization of bio-mechanical limbs for motorial gait rehabilitation, as well as for human gate study and analysis. In particular, the pneumatic actuator has been adopted in this work, representing an alternative solution with respect to the widely used electric motor. This paper proposes also a brief description of the main gait parameters generation as well as the control strategies and architecture. [Copyright &y& Elsevier]

This paper presents a graphical technique to obtain the radius of curvature of the path traced by a coupler point of a planar, single-degree-of-freedom, indeterminate eight-bar linkage commonly referred to as the double flier linkage. The first step is to find the pole for the instantaneous motion of the coupler link; i.e., the point coincident with the absolute instant center of the coupler link. Since the double flier is a linkage with kinematic indeterminacy then the Aronhold–Kennedy theorem cannot locate this instant center. The paper, therefore, begins with a novel technique, which requires few geometric constructions, to locate this instant center. Then the paper focuses on the graphical technique to determine the radius of curvature of the path of an arbitrary coupler point for a given position of the input link. The technique begins by obtaining an equivalent five-bar linkage and four kinematic inversions of this linkage. A four-bar linkage is obtained from each inversion. Finally, the systematic procedure provides a four-bar linkage in which the motion of the coupler link is equivalent up to, and including, the second order properties of motion of the coupler of the original double flier linkage. The radius of curvature of the path traced by the coupler point is then obtained from the well-known Euler–Savary equation. [Copyright &y& Elsevier]

The March 16, 2014 M w 6.7 earthquake played an important role in the complex seismic sequence leading to the nucleation of the April 1st, 2014 M w 8.2 Pisagua earthquake in northern Chile. The M w 6.7, an upper plate reverse faulting event with nodal planes highly rotated counterclockwise with respect to the strike of the megathrust at its location, is analyzed. For each nodal plane of the regional W-phase centroid moment tensor solution, the spatiotemporal slip distribution is inverted using near-field records. The optimal space and time smoothing constraints are determined objectively based on the Akaike's Bayesian Information Criterion. We analyze seismicity on the region affected by the M w 6.7 and M w 8.2 Pisagua mainshock, with accurate hypocenter locations obtained using a 3D heterogeneous medium. We also performed regional moment tensor inversion of events (M ≥ 4.0) occurred before the M w 8.2. Our results suggest the sub-vertical fault plane dipping southward (dip ~ 70°) as being the causative fault of the March 16 M w 6.7 earthquake. The rupture propagated to the northwest, lasted 15 s, and yielded a total seismic moment of 1.36 × 1019 Nm (M w 6.7). Estimated slip is characterized by total rupture length of ~22 km, and suggest shallow slip distributed between ~ 3 km, down to 17 km depth. A comparison between coastal tide gauge records and forward tsunami modeling show similarity of the time series, thus supporting the plausibility of our estimated slip models. Our interpretation suggests that the rupture of the M w 6.7 intraplate could be explained by stress accommodation between two segments along-dip with different mechanical properties at the interplate boundary, and inside the upper plate. • The shallow intraplate March 16, 2014 Mw 6.7 rupture ~22 km length. • Preferred slip model show shallow rupture occurred between ~3 km and 17 km depth. • Sub-vertical fault plane dipping southward (dip ~ 70°) as the causative fault. • Tsunami modeling of the Mw 6.7 event shows plausibility of slip models. [ABSTRACT FROM AUTHOR]

On 18 January 2017, the 2016–2017 central Italy seismic sequence reached the Campotosto area with four events with magnitude larger than 5 in three hours (major event MW 5.5). To study the slip behavior on the causative fault/faults we followed two different methodologies: (1) we use Interferometric Synthetic Aperture Radar (InSAR) interferograms (Sentinel-1 satellites) and Global Positioning System (GPS) coseismic displacements to constrain the fault geometry and the cumulative slip distribution; (2) we invert near-source strong-motion, high-sampling-rate GPS waveforms, and high-rate GPS-derived static offsets to retrieve the rupture history of the two largest events. The geodetic inversion shows that the earthquake sequence occurred along the southern segment of the SW-dipping Mts. Laga normal fault system with an average slip of about 40 cm and an estimated cumulative geodetic moment of 9.29 × 1017 Nm (equivalent to a MW~6). This latter estimate is larger than the cumulative seismic moment of all the events, with MW > 4 which occurred in the corresponding time interval, suggesting that a fraction (~35%) of the overall deformation imaged by InSAR and GPS may have been released aseismically. Geodetic and seismological data agree with the geological information pointing out the Campotosto fault segment as the causative structure of the main shocks. The position of the hypocenters supports the evidence of an up-dip and northwestward rupture directivity during the major shocks of the sequence for both static and kinematic inferred slip models. The activated two main slip patches are characterized by rise time and peak slip velocity in the ranges 0.7–1.1 s and 2.3–3.2 km/s, respectively, and by ~35–50 cm of slip mainly concentrated in the shallower northern part of causative fault. Our results show that shallow slip (depth < 5 km) is required by the geodetic and seismological observations and that the inferred slip distribution is complementary with respect to the previous April 2009 seismic sequence affecting the southern half of the Campotosto fault. The recent moderate strain-release episodes (multiple M~5–5.5 earthquakes) and the paleoseismological evidence of surface-rupturing events (M~6.5) suggests therefore a heterogeneous behavior of the Campotosto fault. [ABSTRACT FROM AUTHOR]