Seismic response of tunnel under normal fault slips by shaking table test technique

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

Late Pleistocene-Holocene slip history of the Langshan-Seertengshan piedmont fault(Inner Mongolia,northern China) from cosmogenic ^(10)Be dating on a bedrock fault scarp

Offset geomorphic features and deformed late Quaternary strata indicate active deformation along the Langshan-Seertengshan piedmont fault （LSPF）, one of the most active faults in the Hetao fault zone in Inner Mongolia, North China. The widespread occurrence of bedrock fault scarps along the LSPF offers excellent opportunity to examine the faulting history. Using cosmogenic ^10Be exposure dating, we measured the exposure ages of the western Langshankou scarp, located in the middle segment of the LSPF. Our data revealed at least two earthquakes that occurred at 22.2±3.3 Ira and 7.2±2.4 ka, respectively. These events are consistent with previous paleoseismic trench studies. The regression of the relationship between the age and sampling height along the scarp yield a fault slip rate of 0.10 ±0.05/-0.06 mm/yr, which is significantly lower than the average post-late Pleistocene fault slip rate of ~1 mm/yr, as estimated from the offset of the T2 terraces by previous studies. This indicates that the slip of the LSPF may have been accommodated by other fault branches.

On the Kinematic Characteristics and Dynamic Process of Boundary faults of the Nansha Ultra-crust Layer-Block

Abstract The Nansha ultra-crust layer-block is confined by ultra-crustal boundary faults of distinctive features, bordering the Kangtai-Shuangzi-Xiongnan extensional faulted zone on the north, the Baxian-Baram-Yoca-Cuyo nappe faulted zone on the south, the Wan'an-Natuna strike-slip tensional faulted zone on the west and the Mondoro-Panay strike-slip compressive faulted zone on the east. These faults take the top of the Nansha asthenosphere as their common detachmental surface. The Cenozoic dynamic process of the ultra-crust layer-block can be divided into four stages: K2-E21, during which the northern boundary faults extended, this ultra-crust layer-block was separated from the South China-Indosinian continental margin, the Palaeo-South China Sea subducted southwards and the Sibu accretion wedge was formed; E22-E31, during which the Southwest sub-sea basin extended and orogeny was active due to the collision of the Sibu accretion wedge; E32-N11, during which the central sub-sea basin extended, the Miri accretion wedge was formed and “A-type” subduction of the southern margin of the north Balawan occurred; N12-the present, during which large-scale thrusting and napping of the boundary faults in the south and mountain-building have taken place and the South China Sea stopped its extension.

Determination of the direction and magnitude of recent tectonic stress in the Xianshuihe fault zone using fault slip data

In this article,a method to determine the complete stress tensor by use of fault slip data in combination with experimental parameters of rock mechanics is elucidated;the direction and magnitude of recent tectonic stress in the Xianshuihe fault zone are determined by this method from a great deal of active fault striae data observed in the fault zone and the envelope of rock fracture determined experimentally for rock samples collected from the fault zone;and the applicability of the method and reliability of calculation results are discussed.

Estimation of the 2001 Kunlun earthquake fault slip from GPS coseismic data using Hori’s inverse method

The Hori＇s inverse method based on spectral decomposition was applied to estimate coseismic slip distribution on the rupture plane of the 14 November 2001 Ms8.1 Kunlun earthquake based on GPS survey results. The inversion result shows that the six sliding models can be constrained by the coseismic GPS data. The established slips mainly concentrated along the eastern segment of the fault rupture, and the maximum magnitude is about 7 m. Slip on the eastern segment of the fault rupture represents as purely left-lateral strike-slip. Slip on the western segment of the seismic rupture represents as mainly dip-stip with the maximum dip-slip about 1 m. Total predicted scalar seismic moment is 5.196× 10^2° N.m. Our results constrained by geodetic data are consistent with seismological results.

Coseismic fault model of the 2017 M_(W)6.5 Jiuzhaigou earthquake and implications for the regional fault slip pattern

On August 8,2017,an M_(W)6.5 earthquake occurred in Jiuzhaigou County,Sichuan Province,China,on the eastern margin of the Qinghai-Tibet Plateau.This study investigates the coseismic deformation field and fault model with ascending and descending Sentinel-1 synthetic aperture radar(SAR)images,aftershock distribution,and elastic half-space dislocation model.The regional fault slip pattern is then quantita-tively examined using the boundary element method.The results show that the ascending and descending interferometric synthetic aperture radar(InSAR)coseismic deformation fields display an overall NNW-SSE trend,with more significant deformation on the southwest side of the fault.The coseismic fault geometry is divided into NW and SE sub-faults with strikes of 162.1°and 149.3°,respectively.The coseismic fault slip is dominated by a left-lateral strike-slip movement with an average rake of-2.31°,mainly occurring at a depth of 0-13.04 km with a shape of an approximately inverted triangle.The fault slip features two peak slip zones,with a maximum of 1.39 m.The total seismic moment is 6.34×10^(18) N·m(M_(W)6.47).The boundary element calculation quantitatively indicates that the regional fault slip pattern may be mainly attributable to the changing strike and dip.The strike changes from NNWeSSE to nearly NS direction,and the dip gradually decreases from the Jiuzhaigou earthquake fault in the north to the Huya fault in the south.With these characteristics,the Huya and the Jiuzhaigou earthquake faults form the eastern boundary of the Minshan uplift zone and accommodate the accumulated deformation.

Co-seismic fault geometry and slip distribution of the 26 December 2004, giant Sumatra–Andaman earthquake constrained by GPS, coral reef, and remote sensing data

We analyze co-seismic displacement field of the 26 December 2004, giant Sumatra–Andaman earthquake derived from Global Position System observations,geological vertical measurement of coral head, and pivot line observed through remote sensing. Using the co-seismic displacement field and AK135 spherical layered Earth model, we invert co-seismic slip distribution along the seismic fault. We also search the best fault geometry model to fit the observed data. Assuming that the dip angle linearly increases in downward direction, the postfit residual variation of the inversed geometry model with dip angles linearly changing along fault strike are plotted. The geometry model with local minimum misfits is the one with dip angle linearly increasing along strike from 4.3oin top southernmost patch to 4.5oin top northernmost path and dip angle linearly increased. By using the fault shape and geodetic co-seismic data, we estimate the slip distribution on the curved fault. Our result shows that the earthquake ruptured ＊200-km width down to a depth of about 60 km.0.5–12.5 m of thrust slip is resolved with the largest slip centered around the central section of the rupture zone78N–108N in latitude. The estimated seismic moment is8.2 9 1022 N m, which is larger than estimation from the centroid moment magnitude（4.0 9 1022 N m）, and smaller than estimation from normal-mode oscillation data modeling（1.0 9 1023 N m）.

Regional Fault Systems of Qaidam Basin and Adjacent Orogenic Belts

The purpose of this paper is to analyze the regional fault systems o f Qaidam basin and adjacent orogenic belts. Field investigation and seismic interp retation indicate that five regional fault systems occurred in the Qaidam and ad jacent mountain belts, controlling the development and evolution of the Qaidam b asin. These fault systems are: (1)north Qaidam Qilian Mountain fault system; (2 ) south Qaidam East Kunlun Mountain fault system; (3)Altun strike slip fault s ystem; (4)Elashan strike slip fault system, and (5) Gansen Xiaochaidan fault s ystem. It is indicated that the fault systems controlled the orientation of the Qaidam basin, the formation and distribution of secondary faults within the basi n, the migration of depocenters and the distribution of hydrocarbon accumulation belt.

Characteristics of the AE Distribution and Triggering Mechanism of a Simulated Meter-Scale Fault after Stick-Slip Events

With the more complete acoustic emission(AE)catalog improved by the multi-channel AE matched-filter technique(MFT),we study the spatiotemporal evolution of the AE activities after laboratory stick-slip events incorporate with the slip data recorded by displacement transducers on an^1.5 m granite fault.The results show that the number of the AE events identified by MFT is about 9 times larger than that of the traditional method.A logarithmic expansion of early AE events along the fault strike is observed as a function of time,whereas the fault does not slip in the same manner.Thus,we related the expansion of the early AE events along the fault to the stress transfer caused by the adjacent AE events.Moreover,there is a good correlation between the cumulative number of the later AE events and the amount of fault slip.It suggests that the stress change caused by the continuous slip of the simulated fault after the stick-slip events response for the later AE events near or on the simulated fault.

Discussion on the Abnormally Low Active Fault Slip Rate of the M_S 8. 0 Wenchuan Earthquake

Based on the collection of active fault slip rate data of large intra-continental shallow thrust earthquakes occurring in the triangular seismic region of the East Asia continent,a preliminary analysis has been performed with results showing that the Wenchuan,Sichuan, China earthquake ( MS = 8.0) of May 12,2008 occurred on the Longmenshan Mountain active fault with an abnormally low slip rate.

Geodetic constraints on contemporary three-dimensional crustal deformation in the Laji Shan—Jishi Shan tectonic belt

The Laji Shan—Jishi Shan tectonic belt(LJTB),located in the southern part of the northeastern Tibetan Plateau(NETP),is a tectonic window to reveal regional tectonic deformation in the NETP.However,its kinematics in the Holocene remains controversial.We obtain the latest and dense horizontal velocity field based on data collected from our newly constructed and existing GNSS stations.Combined with fault kinematics from geologic observations,we analyze the crustal deformation characteristics along the LJTB.The results show that:(1)The Laji Shan fault(LJF)is inactive,and the northwest-oriented Jishi Shan fault(JSF)exhibits a significant dextral and thrust slip.(2)The transpression along the arc-shaped LJTB accommodates deformation transformation between the dextral Riyue Shan fault and the sinistral west Qinling fault.(3)With the continuous pushing of the Indian plate,internal strains in the Tibetan Plateau are continuously transferred in the northeast via the LJTB as they are gradually dissipated near the LJTB and translated into significant crustal uplift in these regions.

Modern tectonic stress field deeply in Xuzhou Coal Mine

By inverting fault slip data, the parameters of 12 tectonic stress tensors in the mine region can be determined. The following characteristics can be obtained for recent tectonic stress fields, which are found deep in the study region. The results show that the recent tectonic stress field mainly presents the characteristics of near NWW-SSE maximum compressional stress and near NE-SW minimum extensional stress, while the stress regimes are mainly of strike slip, part of the reverse-fault type. Recent tectonic stress field in the region is characterized by horizontal components. The maximum principal compression stress direction was from NEE to SEE, the average principal compression stress direction was near NWW-SSE maximum compres- sional stress and near NE-SW minimum extensional. The recent tectonic stress field of the studied area can be controlled by a large tectonic stress area.

Study on a gravity precursor mode of the M_S=7.0 Lijiang earthquake

To study the seismogeny process or the precursory behavior of the 1976 MS=7.0 Lijiang earthquake, we analyze the repeat gravity data with high precision from the Western Yunnan Earthquake Prediction Experiment Area (WYEPEA) and the related results of geology and geophysics survey in this paper. Considering the gross errors caused by observation data and model difference, we have firstly inverted the slip distribution of the main active faults with time based on the robust Bayesian least squares estimation and multi-fault dislocation model. The re-sults show that the slip changes of the faults with time from 1990 to 1997 obviously reflect the preparation process of the Lijiang earthquake. The images of main precursor mode have the characteristic of main shock-after shock type, which is agreement to the model of coupling movement between crust density and crust deformation (DD mode of coupling movement).

The Epi－continental arc of Southeast China and relevant earthquakes

Epi continental arc system is a series of arcuate structures along coastlines of the mainland and behind the island arc system on the margin of the Northwest peri Pacific region. Epi continental arc is similar to the island arc in geometery and kinematics, but it was characterised by an arcuate fracture zone and compensated front sag, basic volcanic activity, shallow earthquake belt and the latest active tectonics. The eastern China continent is dominated by the coastal epi continental arc of Southeast China. Its front arc is situated along the coastline of Zhejiang, Fujian and eastern Guangdong provinces which is convex to SE. The left NW trending flank extended along the NW trending coast line of northern Jiangsu and traversed Shangdong Peninsula to northern Hebei and Shanxi provinces; and the right E W trending flank along the western Guangdong, southern Guangxi, northern Hainan coastlines extended to northern Hanoi. This arc controlls activities of the most modern intense earthquakes in eastern China continents. The compressing thrust type earthquakes occurred along the front arc, especially the 'collison belt', and the strike slip type earthquakes along the both flanks sinistral and dextral strike slip faults respectively. Earthquakes of epi continental arc type is characterised by segmentation in space and periodicity in time.

GNSS deformation characteristics of North China in the past two decades

Based on the Global Navigation Satellite System(GNSS)velocity in North China from 1999 to 2018,the deformation parameters,such as the strain rate,the velocity profiles,and the fault slip rates,are analyzed.The principal conclusions are as follows:1)the GNSS results during 1999-2007 can effectively reflect the deformation characteristics of North China,and the strain rate shows SEE tensile feature in the Shanxi seismic zone with a maximum value of 0.7×10^(-8)/yr.Meanwhile,the deformation is characterized by left-lateral features in the Yinshan seismic zone and Zhangjiakou-Bohai seismic zone with a maximum shear strain rate of 0.7×10^(-8)/yr.2)In the period of 1999-2007,the GNSS velocity profiles show that the deformation is mainly distributed in a range of 100-km width crossing the Yinshan seismic zone and the middle section of the Zhangjiakou-Bohai seismic zone,and 50-km width crossing the Zhangjiakou-Bohai seismic zone near the Bohai Bay.3)The deformation response to the 2011 Japan MW9.0 earthquake shows a significant difference between the middle and east sections of the Zhangjiakou-Bohai seismic zone,and the deformation loading rate decreased from 3.3 mm/yr in 1999-2007 to 2.6 mm/yr and 0.9 mm/yr in the 2013-2018 period for above two sections respectively.Furthermore,the fault slip rates inverted from GNSS measurements show a similar dynamic adjustment process,reflecting the weak impact of the Japan MW9.0 earthquake on the deformation around the central section of the Zhangjiakou-Bohai seismic zone.4)From the results of GNSS strain rate,velocity profile and fault slip rate,we suggest that the potential of the strong earthquake should be high in the Yinshan seismic zone and the middle section of the Zhangjiakou-Bohai fault zone.

Coseismic deformation of the 2020 Yutian MW 6.4 earthquake from Sentinel-1A and the slip inversion

A remarkable earthquake struck Yutian,China on June 26th,2020.Here,we use Sentinel-1 images to investigate the deformation induced by this event.We invert the InSAR observations using a two-step approach:a nonlinear inversion to constrain fault geometries with uniform slip based on the rectangular plane dislocation in an elastic half-space,followed by a linear inversion to retrieve the slip distribution on the fault plane.The results show that the maximum LOS displacement is 22.6 cm,and the fault accessed to the ruptured characteristics of normal faults with the minor left-lateral strike-slip component.The fault model indicates a 210strike.The main rupture zone concentrates in the depth of 5-15 km,and the fault slip peaks at 0.89 m at the depth of 9 km.Then,we calculate the variation of the static Coulomb stress based on the optimal fault model,the results suggest that the Coulomb stress of the Altyn Tagh fault and other neighboring faults has increased and more attention should be paid to possible seismic risks.

Research on the seismotectonics of the Jan－uary 17，1995 Hanshin M7．2 earthquake

Based on the geological tectonics, aftershock activity, earthquake surface rupture and peak ground motion, the geometric and dynamic characteristics of seismogenic tectonics about the 1995 Hanshin earthquake are analysed. Nojima fault and Rokko fault have the same trending direction, but opposite dips. Their rising and falling plates are in symmetrically diagonal distribution. The two faults can be defined as thrust strike slip faults and constitute a pivotal strike slip fault. The earthquake just occurred at the pivot, which is the seismotectonics for the earthquake to develop and occur. The pivotal movement along a strike slip fault often leads to the occurrence of large earthquakes, whose dynamic process can be demonstrated by the stress analysis on the torsion of a beam with rectangle section. The displacement of earthquake surface rupture, aftershock density and peak acceleration change in a certain range of epicentral distance just similar as the shear stress changes from the center to the sides in the rectangle section. The distribution characteristics of the heaviest damage areas are also discussed in the article from the aspects of special geological tectonics and seismotectonic condition. The result obtained from the article can be applied not only to realizing the potencial earthquake sources in middle long time, but also to build reasonably the prediction model about earthquake hazard.

A Review on the Study of "Repeating Earthquakes" by Cross-correlation of Seismic Waveforms

"Repeating earthquakes",identified by cross-correlation of seismic waveforms,are found to be much more abundant in the nature than conventionally expected. In recent years, with the development of digital seismic networks, waveform cross correlation and "repeating earthquakes"have caused much attention to the measuring the variation of crustal medium properties and estimation of location accuracy and fault slip rate at depth or earthquake recurrence intervals. Moreover, as a useful tool, the "repeating earthquake" approach has also been used in the assessment of the accuracy of seismic phase picking,hypocenter location,fault structure and physics of earthquake sources,as well as the study of earthquake prediction. In this paper, we summarized the latest research and applications of "repeating earthquakes".

Crustal Deformation Background Simulation of the Kekexili M_S8.1 Earthquake Happening in 2001

Using the GPS velocity data from 27 stations around the Eastern Kunlun fault as constraints, we first invert the slip velocities of the Eastern Kuniun fault, the north boundary fault of the Qaidam basin, the Mani-Yushu fault and the Margai Caka fault before the Kekexili Ms 8.1 earthquake with a 3-D elastic half-space dislocation model. The deformation field calculated from the slip movement of these faults can be considered the deformation background field of the earthquake. Based on the deformation background field with tectonic implications, we have obtained the strain field and earthquake moment accumulation field. The results show that there are two obvious high moment accumulation rate regions, one of which is the Dongdatan- Xidatan segment of the Eastern Kuniun fault where the Ms8.1 earthquake occurred in 2001.

The Quaternary Tectonic Stress Field of the Kunming Basin and Its Surrounding Areas

The Kunming basin is a Cenozoic faulted basin controlled by N-S trending active faults. there are totally 8 main active faults in and around the Kunming basin area. Inversion of fault slip data suggests that the stress field of the Kunming basin has experienced two major stages. In the first stage ( from the late-Pliocene to mid-Pleistocene),the regional tectonic stress field was characterized by near E-W compression and near N-S extension. In the second stage (from the late-Pleistocene to the present),the tectonic stress field has been mainly characterized by NNW-SSE compression and NEE-SWW extension. Under such a stress field,the near N-S trending faults in the region mainly show a lateral slip.