A novel mitigation measure for normal fault-induced deformations on pile-raft systems

Evidence from recent earthquakes has shown destructive consequences of fault-induced permanent ground movement on structures.Such observations have increased the demand for improvements in the design of structures that are dramatically vulnerable to surface fault ruptures.In this study a novel connection between the raft and the piles is proposed to mitigate the hazards associated with a normal fault on pile-raft systems by means of 3D finite element(FE)modeling.Before embarking on the parametric study,the strain-softening constitutive law used for numerical modeling of the sand has been validated against centrifuge test results.The exact location of the fix-head and unconnected pile-raft systems relative to the outcropping fault rupture in the free-field is parametrically investigated,revealing different failure mechanisms.The performance of the proposed connection for protecting the pile-raft system against normal fault-induced deformations is assessed by comparing the geotechnical and structural responses of both types of foundation.The results indicate that the pocket connection can relatively reduce the cap rotation and horizontal and vertical displacements of the raft in most scenarios.The proposed connection decreases the bending moment response of the piles to their bending moment capacity,verging on a fault offset of 0.6 m at bedrock.

Geometry and 3D seismic characterisation of post-rift normal faults in the Pearl River Mouth Basin,northern South China Sea

Based on high-resolution 3D seismic data acquired in the Pearl(Zhujiang)River Mouth Basin of the northern South China Sea,this study investigated the geometry,spatial extension,and throw distribution of the post-rift normal fault through detailed seismic interpretation and fault modeling.A total of 289 post-rift normal faults were identified in the study area and can be classified into four types:(1)isolated normal faults above the carbonate platform;(2)isolated normal faults cutting through the carbonate platform;(3)conjugate normal faults,and(4)connecting normal faults.Throw distribution analysis on the fault planes show that the vertical throw profiles of most normal fault exhibit flat-topped profiles.Isolated normal faults above the carbonate platform exhibit roughly concentric ellipses with maximum throw zones in the central section whereas the normal faults cutting through the carbonate platform miss the lowermost section due to the chaotic seismic reflections in the interior of the carbonate platform.The vertical throws of conjugate normal faults anomalously decrease toward their intersection region on the fault plane whereas the connecting normal faults present two maximum throw zones in the central section of the fault plane.According to the symmetric elliptical distribution model of fault throw,an estimation was made indicating that normal faults cutting through the carbonate platform extended downward between-1308 s and-1780 s(two-way travel time)in depth and may not penetrate the entire Liuhua carbonate platform.Moreover,it is observed that the distribution of karst caves on the top of the carbonate platform disaccord with those of hydrocarbon reservoirs and the post-rift normal faults cutting through the carbonate platform in the study area.We propose that these karst caves formed most probably by corrosive fluids derived from magmatic activities during the Dongsha event,rather than pore waters or hydrocarbons.

Centrifuge modeling of buried continuous pipelines subjected to normal faulting

Seismic ground faulting is the greatest hazard for continuous buried pipelines.Over the years,researchers have attempted to understand pipeline behavior mostly via numerical modeling such as the finite element method.The lack of well-documented field case histories of pipeline failure from seismic ground faulting and the cost and complicated facilities needed for full-scale experimental simulation mean that a centrifuge-based method to determine the behavior of pipelines subjected to faulting is best to verify numerical approaches.This paper presents results from three centrifuge tests designed to investigate continuous buried steel pipeline behavior subjected to normal faulting.The experimental setup and procedure are described and the recorded axial and bending strains induced in a pipeline are presented and compared to those obtained via analytical methods.The influence of factors such as faulting offset,burial depth and pipe diameter on the axial and bending strains of pipes and on ground soil failure and pipeline deformation patterns are also investigated.Finally,the tensile rupture of a pipeline due to normal faulting is investigated.

Modeling of normal faulting in the subducting plates of the Tonga,Japan,Izu-Bonin and Mariana Trenches:implications for near-trench plate weakening

The plate flexure and normal faulting characteristics along the Tonga, Japan, Izu-Bonin and Mariana Trenches are investigated by combining observations and modeling of elastoplastic deformation of the subducting plate. The observed average trench relief is found to be the smallest at the Japan Trench(3 km) and the largest at the Mariana Trench(4.9 km), and the average fault throw is the smallest at the Japan Trench(113 m) and the largest at the Tonga Trench(284 m). A subducting plate is modeled to bend and generate normal faults subjected to three types of tectonic loading at the trench axis: vertical loading, bending moment, and horizontal tensional force. It is inverted for the solutions of tectonic loading that best fit the observed plate flexure and normal faulting characteristics of the four trenches. The results reveal that a horizontal tensional force(HTF) for the Japan Trench is 33%, 50% and 60% smaller than those of the Mariana, Tonga and Izu-Bonin Trenches, respectively. The normal faults are modeled to penetrate to a maximum depth of 29, 23, 32 and 32 km below the sea floor for the Tonga,Japan, Izu-Bonin and Mariana Trenches, respectively, which is consistent with the depths of relocated normal faulting earthquakes in the Japan and Izu-Bonin Trenches. Moreover, it is argued that the calculated horizontal tensional force is generally positively correlated with the observed mean fault throw, while the integrated area of the reduction in the effective elastic thickness is correlated with the trench relief. These results imply that the HTF plays a key role in controlling the normal faulting pattern and that plate weakening can lead to significant increase in the trench relief.

Fault-Growth Pattern of the South Margin Normal Fault of the Yuguang Basin in Northwest Beijing and its Influencing Factors

Based on high-resolution remote sensing image interpretation, digital elevation model 3-D analysis, field geologic field investigation, trenching engineering, and ground-penetrating radar, synthetic research on the evolution of the Yuguang Basin South Margin Fault （YBSMF） in northwest Beijing was carried out. We found that the propagation and growth of faults most often occurred often at two locations： the fault overlapping zone and the uneven or rough fault segment. Through detailed observation and analysis of all cropouts of faults along the YBSMF from zone a to zone i, we identified three major factors that dominate or affect fault propagation and growth. First, the irregularity of fault geometry determine the propagation and growth of the fault, and therefore, the faults always propagate and grow at such irregular fault segments. The fault finally cuts off and eliminates its irregularity, making the fault geometry and fault plane smoother than before, which contributes to the slipping movement of the half-graben block in the basin. Second, the scale of the irregularity of the fault geometry affects the result of fault propagation and growth, that is, the degree of the cutting off of fault irregularity. The degree of cutting off decreases as irregularity scale increases. Third, the maximum possible slip displacement of the fault segment influences the duration of fault propagation and growth. The duration at the central segments with a large slip displacement is longer than that at the end segments with a smaller slippage value.

Genetic models of structural traps related to normal faults in the Putaohua Oilfield,Songliao Basin

The Putaohua Oilfield is a fault-prolific area and the faults have close relation with structural traps. The genetic models of the structural traps in the Putaohua Oilfield can be divided into two types： individual fault model and multi-fault interaction model. This is based on the description of displacement distribution of typical individual normal faults, the geometry of the footwall and hanging wall, and the analysis of the interaction between faults and the corresponding change in geometry when the faults grow. The individual fault model is that the displacement reaches a maximum at or near the center of fault and decreases toward the fault tips, so a half-graben is formed on the hanging wall of the fault and a half- anticline is formed on the footwall because of the isostatic process. The multi-fault interaction model is that during the growth of faults, they overlap and interact with each other, and accommodation zones are formed in the overlapping segments. The accommodation zones are favorable targets for hydrocarbon exploration, and the trap characteristics are dependent The multi-fault interaction model can be subdivided on the extent of overlap and occurrence of faults. into three types： synthetic accommodation zone, convergent accommodation zone and divergent accommodation zone. Hydrocarbon migration and accumulation models of each type have been developed. The hydrocarbon migration and accumulation models of the traps with different genetic models have their own characteristics in the different stages of fault growth.

Normal Faulting Type Earthquake Activities in the Tibetan Plateau and Its Tectonic Implication

This paper analyzes various earthquake fault types, mechanism solutions, stress field as well as other geophysical data to study the crust movement in the Tibetan plateau and its tectonic implications. The results show that a lot of normal faulting type earthquakes concentrate in the central Tibetan plateau. Many of them are nearly perfect normal fault events. The strikes of the fault planes of the normal faulting earthquakes are almost in the N-S direction based on the analyses of the equal area projection diagrams of fault plane solutions. It implies that the dislocation slip vectors of the normal faulting type events have quite great components in the E-W direction. The extension is probably an eastward extensional motion, mainly a tectonic active regime in the altitudes of the plateau. The tensional stress in the E-W or WNW-ESE direction predominates the earthquake occurrence in the normal event region of the central plateau. A number of thrust fault and strike-slip fault type earthquakes with strong compressive stress nearly in the NNE-SSW direction occurred on the edges of the plateau. The eastward extensional motion in the Tibetan plateau is attributable to the eastward movement of materials in the upper mantle based on_seismo-tomographic results. The eastward extensional motion in the Tibetan plateau may be related to the eastward extrusion of hotter mantle materials beneath the east boundary of the plateau. The northward motion of the Tibetan plateau shortened in the N-S direction probably encounters strong obstructions at the western and northern margins. Extensional motions from the relaxation of the topography and/or gravitational collapse in the altitudes of the plateau occur hardly in the N-S direction. The obstruction for the plateau to move eastward is rather weak.

Normal Fault Slips of the March 2021 Greece Earthquake Sequence from InSAR Observations

In March 2021,a seismic sequence including three Mw>5.5 events struck northern Thessaly,Greece.Owing to the high temporal resolution of Sentinel-1 images which were sampled every 6 days and recorded the three events separately,we are able to map individually the coseismic deformation fields of the three events.Based on their respective coseismic displacements,we determined the geometry of the fault plane for each earthquake with the method of multipeak particle swarm optimization and inverted the best-fitting slip distribution by linear least squares inversion.Modelling results show that the three events occurred successively on 3,4 and 12 March 2021 were all dominated by normal-slip motions on previously unknown faults within the top 15 km of the Earth’s crust.The 3 March 2021 Mw 6.3 earthquake ruptured a northeast-dipping fault with a strike angle of 301°(clockwise from the North)and a dip angle of 46°,producing the maximum slip of about 2.2 m.The slip motion of the 4 March 2021 Mw 5.9 aftershock shows a similar fault geometry(striking 297°and dipping 42°)to the 3 March mainshock,but with a considerably smaller dip-slip component(~0.8 m).The 12 March 2021 Mw 5.6 aftershock occurred on a southwest-dipping fault(striking 100°and dipping 40°)with a normal fault slip of up to 0.5 m.Static Coulomb stress changes triggered by the earthquake sequence imply a promotion relationship between the first 3 March event and the two subsequent events.Due to the coseismic stress perturbation,more than 70%of aftershocks were distributed in areas with increased Coulomb stress and the northwest segment of the Larissa fault close to the seismic sequence was exposed to a relatively high seismic risk.

Power-law Distribution of Normal Fault Displacement and Length and Estimation of Extensional Strain due to Normal Faults:A Case Study of the Sierra de San Miguelito, Mexico

The Sierra de San Miguelito is a relatively uplifted area and is constituted by a large amount of silicic volcanic rocks with ages from middle to late Cenozoic. The normal faults of the Sierra de San Miguelito are Domino-style and nearly parallel. The cumulative length and displacement of the faults obey power-law distribution. The fractal dimension of the fault traces is -1.49. Using the multi-line one-dimensional sampling, the calculated exponent of cumulative fault displacements is -0.66. A cumulative curve combining measurements of all four sections yielded a slope of -0.63. The displacement-length plot shows a non-linear relationship and large dispersion of data. The large dispersion in the plot is mainly due to the fault linkage during faulting. An estimation of extensional strain due to the normal faults is ca. 0.1830. The bed extension strain is always less than or equal to the horizontal extension strain. The deformation in the Sierra de San Miguelito occurred near the surface, producing pervasive faults and many faults are too small to appear in maps and sections at common scales. The stretching produced by small faults reach ca. 33% of the total horizontal elongation.

Influence factors on the ground surface rupture zone induced by buried normal fault dislocation

The seismic disaster presents a zonal distribution along the fault strike.In this paper,rupture zone of ground surface soil caused by the uniform dislocation,inclined dislocation and warped dislocation of buried normal fault are studied by constituting a three-dimensional finite element model in Automatic Dynamic Incremental Nonlinear Analysis(ADINA).According to the critical value of surface rupture,the variational features and influencing factors of width and starting position of the"avoiding zone"in engineering construction are analyzed by using 96 model calculations.The main results are as follows:(1)Since the rupture zone of the ground surface soil from the point of mechanics is different from the"avoidance zone"from the point of engineering safety,the equivalent plastic strain and the total displacement ratio should be considered to evaluate the effect of the seismic ground movement on buildings.(2)During fault dislocation,plastic failure firstly occurred on the ground surface soil of the footwall side,and then the larger deformation gradually moved to the side of the hanging wall of the fault with the increase of fault displacement.(3)When the vertical displacement of buried fault reaches 3 m,the width of"avoiding zone"in engineering construction varies within the range of 10-90 m,which is most affected by the thickness of overlying soil and the dip angle of the fault.

A model test on an open-cut tunnel structure under the effect of a stick-slip normal fault

Purpose–Large displacement misalignment under the action of active faults can cause complex threedimensional deformation in subway tunnels,resulting in severe damage,distortion and misalignment.There is no developed system of fortification and related codes to follow.There are scientific problems and technical challenges in this field that have never been encountered in past research and practices.Design/methodology/approach–This paper adopted a self-designed large-scale active fault dislocation simulation loading system to conduct a similar model test of the tunnel under active fault dislocation based on the open-cut tunnel project of the Urumqi Rail Transit Line 2,which passes through the Jiujiawan normal fault.The test simulated the subway tunnel passing through the normal fault,which is inclined at 608.This research compared and analyzed the differences in mechanical behavior between two types of lining section:the opencut double-line box tunnel and the modified double-line box arch tunnel.The structural response and failure characteristics of the open-cut segmented lining of the tunnel under the stick-slip part of the normal fault were studied.Findings–The results indicated that the double-line box arch tunnel improved the shear and longitudinal bending performance.Longitudinal cracks were mainly distributed in the baseplate,wall foot and arch foot,and the crack position was basically consistent with the longitudinal distribution of surrounding rock pressure.This indicated that the longitudinal cracks were due to the large local load of the cross-section of the structure,leading to an excessive local bending moment of the structure,which resulted in large eccentric failure of the lining and formation of longitudinal cracks.Compared with the ordinary box section tunnel,the improved double-line box arch tunnel significantly reduced the destroyed and damage areas of the hanging wall and footwall.The damage area and crack length were reduced by 39 and 59.3%,respectively.This indicates that the improved double-line box arch tunnel had good anti-sliding performance.Originality/value–This paper adopted a self-designed large-scale active fault dislocation simulation loading system to conduct a similar model test of the tunnel under active fault dislocation.This system increased the similarity ratio of the test model,improved the dislocation loading rate and optimized the simulation scheme of the segmented flexible lining and other key factors affecting the test.It is of great scientific significance and engineering value to investigate the structure of subway tunnels under active fault misalignment,to study its force characteristics and damage modes,and to provide a technical reserve for the design and construction of subway tunnels through active faults.

Influences of pre-existing fracture on ground deformation induced by normal faulting in mixed ground conditions

Physical model tests have been conducted by various researchers to investigate fault rupture propagation and ground deformation induced by bedrock faulting. However, the effects of pre-existing fracture on ground deformation are not fully understood. In this work, six centrifuge tests are reported to investigate the influence of pre-existing fracture on ground deformation induced by normal faulting in sand, clay and nine-layered soil with interbedded sand and clay layers. Shear box tests were conducted to develop a filter paper technique, which was adopted in soil model preparation to simulate the effects of pre-existing fracture in centrifuge tests. Centrifuge test results show that ground deformation mechanism in clay, sand and nine-layered soil strata is classified as a stationary zone, a shearing zone and a rigid body zone. Inclination of the strain localization is governed by the dilatancy of soil material. Moreover, the pre-existing fracture provides a preferential path for ground deformation and results in a scarp at the ground surface in sand. On the contrary, fault ruptures are observed at the ground surface in clay and nine-layered soil strata.

Late Cenozoic Normal Faulting on the Western Side of Wenquan Graben, Central Qianghai-Xizang(Tibet) Plateau

A near NS-strike east-dipping normal fault is developed on the western side of Wenquan graben in the central Qinghai-Xizang(Tibet) Plateau. It is the western marginal fault of the graben and has been intensely active. It is a product of the near EW extension and deformation of the central northern Qinghai-Xizang(Tibet) Plateau since the late Cenozoic under the effect of the collision of the India and Eurasia plates. Since the late Cenozoic, the maximum vertical displacement on the fault was greater than 2.1km, and the dislocated Mesozoic fold stratum reveals a maximum accumulative throw of 6.0±2.2km. Quaternary faulting took place many times along the fault, creating multi-set piedmont fault facets and multi-level fault scarplets. According to the height of fault scarps that result from the vertical offset of the late Quaternary strata and geomorphic provinces, the maximum slip rate of the fault is estimated to have been less than 1.2mm/a since the late Quaternary, averaging 0.45mm/a. The trenching across the fault reveals that at least 3 paleoearthquakes of varied magnitudes have occurred since the late Epipleistocene. In view of the characteristics of Cenozoic faulting, it is concluded that the fault will act as a dominant seismogenic fault for earthquakes of M6.0 to M7.0 that are most likely to occur in the future.

Convex-up Style of Deformation within Grabens in Regions of Incomplete Crossing Conjugate Normal Faults: A Numerical Simulation Investigation and Case Study

Crossing conjugate normal faults(CCNFs)are extensively developed in many hydrocarbon-producing basins,generally existing in the form of incomplete CCNFs.Nevertheless,the effect of the non-conjugate zone of the CCNFs on the conjugate relay zone post late tectonic action has not been previously studied.We use 3D elastic-plastic modeling to investigate the influence of incomplete(i.e.,partially intersecting)CCNFs on the pattern of deformation of strata in the intersection region.A series of model simulations were performed to examine the effects of horizontal tectonic extension,fault size,and fault depth on the deformation of conjugate relay zones of incomplete CCNFs.Our analyses yielded the following results.(1)The model of incomplete conjugation predicts a convex-up style of deformation in the conjugate graben region superimposed on overall subsidence under applied horizontal tectonic extension.(2)The degree of convex-up deformation of the conjugate graben depends on the influence of the non-conjugate zone on the conjugate relay zone,which varies with the amount of horizontal tectonic extension,fault size,and fault burial depth.(3)Our results indicate that incomplete CCNFs can form convex-up deformation,similar to that in the Nanpu Sag area and provide a sound understanding of hydrocarbon migration and accumulation.

Prediction of vertical displacement for a buried pipeline subjected to normal fault using a hybrid FEM-ANN approach

Fault movement during earthquakes is a geotechnical phenomenon threatening buried pipelines and with the potential to cause severe damage to critical infrastructures.Therefore,effective prediction of pipe displacement is crucial for preventive management strategies.This study aims to develop a fast,hybrid model for predicting vertical displacement of pipe networks when they experience faulting.In this study,the complex behavior of soil and a buried pipeline system subjected to a normal fault is analyzed by using an artificial neural network(ANN)to generate predictions the behavior of the soil when different parameters of it are changed.For this purpose,a finite element model is developed for a pipeline subjected to normal fault displacements.The data bank used for training the ANN includes all the critical soil parameters(cohesion,internal friction angle,Young’s modulus,and faulting).Furthermore,a mathematical formula is presented,based on biases and weights of the ANN model.Experimental results show that the maximum error of the presented formula is 2.03%,which makes the proposed technique efficiently predict the vertical displacement of buried pipelines and hence,helps to optimize the upcoming pipeline projects.

Three-dimensional S-wave velocity structure of the crust and upper mantle for the normal fault system beneath the Yinchuan Basin from joint inversion of receiver function and surface wave

A series of parallel normal faults are distributed in the Helan Mountain-Yinchuan Basin tectonic belt,where a historical M8.0 earthquake occurred.It is rare that such a great earthquake occurs in a normal fault system within the continent.To deeply understand the fine structure of the normal fault system,we deployed 104 broadband temporary stations near the system,collected data from permanent stations and other temporary stations nearby,and obtained the high-precision threedimensional S-wave velocity structure beneath 206 stations via joint inversion of receiver function and surface wave.A typical graben-in-graben feature bounded by four major faults was identified in the Yinchuan Basin.We analyzed the seismicity in the normal fault system and found a seismic strip in the southern part of the basin,where there are significant changes in the sedimentary thickness,which is speculated to be the southern boundary of the normal fault system.There are significant differences in the crustal thickness and velocity structure in the crust on both sides of the boundary between the Helan Mountain and the Yinchuan Basin,and a low-velocity zone was identified in the upper mantle beneath this boundary,which could be related to the fact that the Helan Mountain-Yinchuan Basin tectonic belt is located between the Alxa Block and the Ordos Block.The M8.0 Yinchuan-Pingluo earthquake occurred at the junction of four major faults in the Yinchuan Basin,which was located in the high-velocity zone near the velocity transition zone at the basin-mountain boundary.The low-velocity zone in the upper mantle beneath this boundary may have promoted the nucleation of this earthquake.Based on evidence from geological drilling,micro seismicity,the regional stress field,and the velocity models obtained in this study,it is inferred that the eastern piedmont fault zone of the Helan Mountain was the seismogenic fault of the 1739 M8.0 Yinchuan-Pingluo earthquake.

Gravity Fault Subsidence and Beach Ridges Progradation in Quinta-Cassino (RS) Coastal Plain, Brazil

Ground penetrating radar (GPR) surveys have being applied to investigate very near-surface stratification of sedimentary units in coastal plains and to define their depositional conditions. This paper presents, however, low-frequency GPR survey to investigate fault-related depositional systems at greater depths. The Quinta-Cassino area in the Rio Grande do Sul Coastal Plain (RGSCP, Brazil) shows a wide strandplain that is made off by very long, continuous, and linear geomorphic features (beach ridges). This strandplain extends for ~70 km southward. The beach ridges show low-angle truncations against the Quinta escarpment, and also truncations in the strandplain. The traditional approach points that RGSCP was developed by juxtaposition of four lagoons/barrier systems as consequence of sea level changes;previous model assumes that no deformational episode occurred in RGSCP. The geophysical and geological surveys carried out in this area showed the existence of listric fault controlling the beach ridges in the escarpments and hanging-wall blocks. The radargrams could distinguish Pleistocene basement unit anticlockwise rotation, thickening of beach ridges radarfacies close to listric normal faults, and horst structures. These deformational features indicate that the extensional zone of a large-scale gravity-driven structure controlled the mechanical subsidence, the Holocene sedimentation and its stratigraphic and geomorphic features in the Quinta-Cassino area to build up an asymmetric delta. The results point to a new approach in dealing with RGSCP Holocene evolution.

First Discovery of North-South Striking Normal Faults near the Potential Eastern End of Altyn Tagh Fault

The Altyn Tagh fault is the northern boundary of Tibetan Plateau. As one of the most well-known strike-slip fault in the world, great achievements on tectonic deformation and Late Qua- ternary slip rate have been made. However, there is a long-lasting debate on whether the Altyn Tagh fault extends into the Jinta Basin or even eastward. In this paper, we use satellite image interpretation, field investigation, trench excavation, and optical stimulated luminescence dating to study newly found NS striking scarps in the eastern end of Jinta Nan Shan. The results are as follows： firstly, a group of normal faults develop on terrace T2 of Heihe River, the total length amounts to -40 km, total scarp height is 304-5 m; secondly, four paleoseismic events have been interpreted from three trenches, approximate ages of events are 79.97±19.14 ka BP, 62.55±13.10~55.41±10.77 ka BP, before 16.89±2.08 ka BP, 8.52±1.49 ka BP, respectively; thirdly, just like NS normal faults in the western end of Altyn Tagh fault, the newly found NS extensional faults are likely the terminating tectonics of the eastern end of Altyn Tagh fault, the large Altyn Tagh fault may end in the eastern end of Jinta Nan Shan.

Three-dimensional finite difference analysis of shallow sprayed concrete tunnels crossing a reverse fault or a normal fault: A parametric study

Urban tunnels crossing faults are always at the risk of severe damages.In this paper,the efects 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,theleffects 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.

Relationship between Landslides and Active Normal Faulting in the Epicentral Area of the AD 1556 M～8.5 Huaxian Earthquake,SE Weihe Graben(Central China)

In this paper, we focus on the characteristics of the landslides developed in the epicentral area of AD 1556 M^8.5 Huaxian Earthquake, and discuss their relations to the active normal faults in the SE Weihe Graben, Central China. The results from analyzing high-resolution remote-sensing imagery and digital elevation models（DEMs）, in combination with field survey, demonstrate that：（i） the landslides observed in the study area range from small-scale debris/rock falls to large-scale rock avalanches;（ii） the landslides are mostly developed upon steep slopes of ≥30°; and（iii） the step-like normal-fault scarps along the range-fronts of the Huashan Mountains as well as the thick loess sediments in the Weinan area may facilitate the occurrence of large landslides. The results presented in this study would be helpful to assess the potential landslide hazards in densely-populated areas affected by active normal faulting.