A Study of Seismic Anisotropy of Wenchuan Earthquake Sequence

Gao, Yuan; Zhao, Chen; Yao, Zhixiang; Ling-xue, Tai

doi:10.1002/cjg2.1335

Cited by 17 publications

(18 citation statements)

References 16 publications

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“…Historically, seismicity on the SW segment is high since late Pleistocene, but it is weak on the NE segment since Quaternary. Sheer wave splitting research of aftershocks of Wenchaun M8.0 earthquake also reveals that the principal compressional stress varied remarkably on the two segments [11]. Based on the comprehensive analysis of the satellite imagery, geological documents, historical seismicity, as well as the Bouguer gravity anomalous, geomorphic features and fault activity investigation, Chen et al [12] pointed out that the NS striking Huya and Leidong faults intersect with the Longmenshan fault zone on the MianzhuAnxian section and divide the Longmenshan fault zone into SW and NE segments.…”

Section: Discussionmentioning

confidence: 94%

Rupture process of the Wenchuan M8.0 earthquake of Sichuan China: the segmentation feature

et al. 2009

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Moment tensor solution, rupture process and rupture characteristics of the great Wenchuan M8.0 earthquake are studied by using 39 long-period P and SH waveforms with evenly azimuth coverage of stations. Our results reveal that the Wenchuan M8.0 event consisted of 5 sub-events of M w ≥7.3 occurring succesively in time and space. Rupture started with a M w 7.3 introductory strike-slip faulting in the first 12 s, then within 12−40 s, two sub-events with M w 7.6 and M w 7.4 occurred within 80 km northeast from the initial point with the dominant rupture type of thrust moving. From 40 to 62 s, a M w 7.5 and M w 7.4 right-lateral strike-slip type of sub-events occurred on the two sides of Beichuan, 120 km away northeast from the initial point. The whole rupture process lasted 105 s and unilaterally propagated from the initial point on the WS section of the Yingxiu-Beichuan fault to the NE direction, resulting in a 230-km-long surface rupture zone and the average surface dislocation is up to 4 m. Two asperities are identified and the whole rupture process is formed by WS and NE parts. In the WS part named Dujiangyang-Wenchuan, where the initial point is located, the rupture process showed reverse faulting with the maximum slip of 8.2 m. Around Mianzhu, rupture changed to right-lateral strike slip faulting and formed a Beichuan-Qingchuan large slip area. The rupture area on this part is about 10 km in depth, shallower than on the WS part. The maximum slip is 6.53 m. Consequently, there formed 2 segments with the surface dislocation larger than 6 m. One is the Dujiangyan-Wenchuan segment with the maximum surface displacement of 6.44 m, the other is the Beichuan-Qingchuan segment with the maximum surface displacement of 6.53 m. This segmentation may have its geological and tectonic background. Wenchuan earthquake, moment tensor solution, rupture process, fault segmentation characteristics Citation: Zhao C P, Chen Z L, Zhou L Q, et al. Rupture process of the Wenchuan M8.0 earthquake of Sichuan, China: the segmentation feature.At 14:28 on May 12, 2008, a great earthquake occurred in Wenchuan County of Sichuan Province, China. It caused the most severe damage and affected the largest area among other earthquakes since New China was founded, and resulted in tremendous injuries and deaths, as well as disaster. Study on its source rupture process using the digital seismic waveform data can provide information about the rupture scale, the way of fault moving, as well as slip distribution on the fault within several hours after a strong earthquake occurred. These estimations can not only rapidly provide the information on the seriously damaged area and the way of dislocation as well as important information for estimating the destructed scale and doing rescue work, but can also provide important information about the activity of the causative fault and the tendency of the earthquake sequence. After the Wenchuan M8.0 earthquake occurred, several research groups immediately carried out the source rupture process inversion. We also e...

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Section: Discussionmentioning

confidence: 94%

Rupture process of the Wenchuan M8.0 earthquake of Sichuan China: the segmentation feature

et al. 2009

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“…The predominant polarization of fast shearwaves strikes to ENE, consistent with the polarization obtained by Rau et al [17] with S wave, but different from the direction of regional principal compressive stress and strain, and also different from the fault strike. Some researches indicate that complicated local structures or fracture distribution can lead to the stress complication, and may produce significant difference in anisotropy on both sides of the fault [8] , especially when the station is near a strike-slip fault, the polarization is consistent with the fault strike [6,7,29] , but because Xiaoyoukeng fault is a normal fault, whether or not the fault influences the polarization direction need more research. Station NCU is on ENE striking Shuanglianpo fault, which is a reverse fault.…”

Section: Resultsmentioning

confidence: 99%

Crustal Anisotropy in North Taiwan from Shear‐Wave Splitting

Ling-xue

Gao

Fong

et al. 2011

Chinese J of Geophysics

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Using the seismic data recorded by 13 seismic stations in north Taiwan from July 1991 to December 2002, this study analyzes the feature of shear‐wave splitting in north Taiwan by SAM method of shear‐wave splitting. The results show that predominant polarization directions of fast shear‐waves at Yilan basin strikes to nearly E‐W, while polarization directions at mountain ranges (Western Foothill, HsüCeshan Range and Central Range) are in NNE or NE direction. Polarizations are scattered if the stations are on seashore or on island, and often have two predominant polarizations, which may be caused by irregular topography or complicated local tectonics. From the spatial distribution of time delays, we also find that taking station TWE as a boundary, time delays at station TWE and north of the station are longer than those at south of the station. It possibly suggests that anisotropy at station TWE and north of the station are stronger than anisotropy at south of the station.

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“…The method is mainly based on polarization analysis [20], with the addition of correlation analysis and a time delay deduction technique [33]. Many studies [22][23][24][34][35][36][37][38] attest to the dependable results of SAM.…”

Section: Methodsmentioning

confidence: 99%

Crust-mantle coupling in North China: Preliminary analysis from seismic anisotropy

Gao

2010

Chin. Sci. Bull.

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Seismology) are compared with data from a temporary North China Seismic Array to obtain the background orientation of the horizontal crustal principal compressive stress at NE 95.1°±15.4° in North China. Data are corrected for disturbances of faults and irregular tectonics, and are used to constrain the fast SKS polarization at NE 110.2°±15.8° in North China. Individual station analyses suggests that there is consistently more than 10° difference between the polarizations of fast shear-wave in the crust and those of fast SKS phases. Azimuthally anisotropic phase velocities of Rayleigh waves at different periods also indicate an orientation change for fast velocity with depth. It suggests the crust-mantle coupling in North China follows neither the simple decoupling model nor the strong coupling model. Instead, it is possibly some inhomogeneous combination of two models or some gradual-change model of physical characteristics. This study shows that anisotropy in the crust and mantle could be multiply characterized more correctly and crust-mantle coupling could be analyzed further, if increasing near-field shear-wave splitting data that indicate crustal anisotropy, combined with the azimuthal anisotropy of Rayleigh waves, besides the result of SKS splitting travelling through lithosphere and surface GPS measurements. seismic anisotropy, crust-mantle coupling, polarization direction of fast shear-wave, shear-wave splitting, crustal principal compressive stress, North China Citation:Gao Y, Wu J, Yi G X, et al. Crust-mantle coupling in North China: Preliminary analysis from seismic anisotropy.

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A Study of Seismic Anisotropy of Wenchuan Earthquake Sequence

Cited by 17 publications

References 16 publications

Rupture process of the Wenchuan M8.0 earthquake of Sichuan China: the segmentation feature

Rupture process of the Wenchuan M8.0 earthquake of Sichuan China: the segmentation feature

Crustal Anisotropy in North Taiwan from Shear‐Wave Splitting

Crust-mantle coupling in North China: Preliminary analysis from seismic anisotropy

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