The 2016 MW7.8 Kaikoura earthquake struck the northern part of south Island, New Zealand, within the active and complex Australia–Pacific plate boundary system. Firstly, we used the InSAR method to obtain coseismic LOS deformation fields based on SAR images and applied offset tracking methods to obtain offset measurements based on optical satellite images. The maximum displacement of about 6 m is detected in the direction away from the satellite on the south-west side and also towards the satellite on the north-east side. The 3D deformation field is then resolved by the combination of these measurements with a least-square solve method, and comparisons with 3 components of GPS stations show good consistency. Despite complex features demonstrated in the 3D deformation field, there are still clear spatial correlations between surface deformation and faults distribution. It reveals that more than ten faults were ruptured during the earthquake, including some faults were previously understudies for their tectonic activities. The maximum horizontal deformation of about 10 m occurs along the Kekerengu fault with the vertical deformation up to 2 m. The 3D deformation shows that the mainshock is a multi-segments faulting with a rupture process of strike-slip, compression, transpressional rupture and strike-slip in space along the NE direction.

Tectonic research of the Tibetan Plateau has long focused on its deformation style and mechanisms. The 2008 Mw7.9 Wenchuan earthquake ruptured the Longmen Shan fault located at the eastern rim of the plateau and excited a viscoelastic response of the lithosphere. We infer a three‐dimensional (3D) rheological structure of eastern Tibet from modeling nine years of postseismic displacements observed by GPS. Our solution provides tight constraints on the lower‐crustal and upper‐mantle steady‐state viscosities of the Songpan‐Ganzi Terrane as (5.0 ± 0.7) × 1018 and (1.3 ± 0.3) × 1019 Pa s, respectively, consistent with a “jelly sandwich” model of Tibet, but not with some crustal channel flow models featuring much lower viscosities. The inferred lower‐crustal and upper‐mantle transient viscosities are (5.0 ± 1.3) × 1017 and (5.0 ± 1.5) × 1018 Pa s, respectively, suggesting nonlinear deformation mechanisms. The adjacent West Qinling and Sichuan blocks feature an order‐of‐magnitude higher rheological strength, which is consistent with the changes in the crustal material properties and interseismic deformation style across the East Kunlun‐Tazang and Longmen Shan faults. Our results enable us to propose a conceptual 3D tectonic deformation model, in which the eastward extrusion of Tibet is absorbed in the Songpan‐Ganzi crust mainly by E‐W shortening and N‐S extension, accommodated through faulting of conjugate strike‐slip faults in the upper crust and distributed shear in the lower crust.

阿尔金断裂是中国大陆内部一条重要断裂带,对理解青藏高原的隆升演化和大陆构造变形过程均有重要意义,其滑动速率的争议也成为理解这一问题的关键.本文汇总了近年来关于阿尔金断裂滑动速率绝大部分究成果,包含了82°E?99°E范围内来自一般地质学、古地震和大地测量的结果,覆盖了几十年、千年和万年以上的时间尺度和整个阿尔金断裂带,形成对阿尔金断裂带滑动速率的时空变化特征的全面认识,迄今为止的研究结果均支持阿尔金断裂中西段具有(10±3)mm/a的滑动速率,自约93°E向东逐渐衰减,且随时间变化不大,由于测量方法导致的差异可能与一次大地震或地震高发期有关.

In a viscoelastic Earth, stresses slowly built up due to fault locking are relaxed concurrently during the entire interseismic period. This interseismic stress relaxation causes crustal deformation much farther away from the locked fault than can be explained using elastic models that neglect the relaxation. Here we develop a viscoelastic geodetic inversion model to address this problem at Cascadia. We invert ~500 horizontal velocity vectors based on continuous and campaign geodetic measurements over the past two decades. Ambiguities arising from long‐term rotation of upper‐plate crustal blocks are addressed by test‐correcting the geodetic velocities with two different block‐motion models. Fault back slip (i.e., slip deficit) Green's functions are derived using a Maxwell viscoelastic finite element model with realistic subduction zone structure and megathrust geometry. The preferred model features a narrow and shallow megathrust locked zone, consistent with earlier thermorheological reasoning. For an elastic model to fit the data to the same fidelity, megathrust locking has to extend to much greater depths. However, even with the viscoelastic model, the land‐based geodetic data still cannot resolve whether there is some creep (incomplete locking) in the shallowest part of the megathrust far offshore. Neither can the land data fully resolve along‐strike variations of the locking state. These ambiguities can be resolved only when adequate seafloor geodetic data are obtained.

It has been debated for decades whether crustal deformation in and around the Tibetan plateau is distributed or block-like. We model crustal deformation in northeastern Tibet using a deformable-block-motion model, in which kinematic parameters of block motion and internal deformation and the associated boundary slip rates are inverted for using GPS velocity data. The F-test is used to screen out station velocity outliers, justify independence of neighboring blocks, and determine the significance of block internal strains through an iteration process. As a result, fifteen blocks are identified, with their boundary faults slipping at rates of 1-10 mm/a. Blocks located east and north of the plateau have large sizes (>10(4) km(2) in area) in general, with little internal deformation. Six blocks within the plateau, in contrast, are smaller in sizes, with internal strain rates on the order of 1-10 nanostrain/a. Five blocks sitting at the northeast borderland of the plateau have small block sizes but no significant internal deformation. Our results show sinistral slip rates of 4.3 +/- 1.6 and 4.6 +/- 1.8 mm/a across the western and eastern segments of the Haiyuan fault, and 10.8 +/- 2.3, 4.6 +/- 2.6, and 3.8 +/- 2.1 mm/a across the western, central, and eastern segments of the East Kunlun fault, respectively. The southwestern, central, and northeastern segments of the Longmenshan fault slip right-laterally at rates of 1.7 +/- 1.1, 1.1 +/- 0.8, and 1.1 +/- 0.8 mm/a, with shortening rates of 1.1 +/- 1.2, 0.4 +/- 0.8, and 0.8 +/- 1.1 mm/a, respectively. We also develop a scheme to convert geodetic strain rate into seismic moment accumulation rate within blocks and at block boundaries, and estimate the two rates as,similar to 8.40 x 10(18) and similar to 2.06 x 10(19) N.m/a, respectively. In comparison, the corresponding seismic moment release rates are estimated as similar to 6.06 x 10(18) and similar to 2.44 x 10(19) N.m/a using an contemporary earthquake catalog of 1920-2015. Such results indicate that the seismic moment accumulation and release rates are comparable for the latest 95 years when the earthquake catalog is complete for strong to large events. Both geodetic and seismic estimates suggest that a major portion (similar to 70-80%) of the total seismic moment is accumulated and released at block boundaries, and a minor but still significant portion (similar to 20-30%) is accumulated and released within blocks. (C) 2017 The Author(s). Published by Elsevier Ltd.

龙门山断裂带系统位于青藏高原东缘，是有关青藏高原大陆地壳形变模式争论备受关注的焦点地区。对其地震轮回期间地壳内应力应变场的时空演化的模拟研究，不仅有助于深入理解龙门山断裂带现今运动的动力学机制与汶川地震成因，同时对于论证青藏高原东缘的活动构造形变模式及相应的动力学过程具有重要意义。

We estimate the seismic hazard potential in the Sichuan-Yunnan region, western China using three different approaches. Our first approach, based on the assumption that the earthquake probability is proportional to the past seismicity rate, uses a regional earthquake catalog to constrain the probability model. A retrospective test shows that the 'forecasts' have some predictive power for strong events occurred on fault segments with shorter earthquake recurrence time, but not for that with longer recurrence time such as the Longmenshan fault. Our second approach, based on the assumption that the earthquake probability is proportional to crustal strain rate, uses secular geodetic strain rate deduced from GPS velocity data to constrain the probability model. A retrospective test of the model with earthquake occurrence of the past 30 years shows that the model 'forecasted' poorly. However, the model seems to 'forecast' spatial intensity of earthquakes for the past 500 years reasonably well, suggesting that the geodetic strain rate obtained at the decadal scale may still be a good indicator of long term earthquake activity in the region, but only at a time scale of hundreds of years. Our third approach uses GPS velocity data to determine the seismic moment accumulation rates on major faults, and a historical earthquake catalog to estimate seismic moments released in the past. Comparison of the two yields estimates of present day seismic moments cumulated on major faults, and a retrospective test shows some predictive power of the method. Our result suggests that numerous faults in the Sichuan-Yunnan region have cumulated seismic moments capable of producing M > 7.5 earthquakes, including the Xiaojiang, Jiali, Northern Nujiang, Nandinghe, and Red River-Puer faults, and the junction fault between the Xianshuihe and Ganzi-Yushu faults. (C) 2015 Elsevier Ltd. All rights reserved.

Research Article| January 01, 2014 Coulomb Stress Change and Evolution Induced by the 2008 Wenchuan Earthquake and its Delayed Triggering of the 2013 Mw 6.6 Lushan Earthquake Yanzhao Wang; Yanzhao Wang aState Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, Chinawangyz0513@gmail.commwang@gps.gov.cn Search for other works by this author on: GSW Google Scholar Fan Wang; Fan Wang bNational Geomatics Center of China, Beijing 100830, Chinawangfan0003@gmail.com Search for other works by this author on: GSW Google Scholar Min Wang; Min Wang aState Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, Chinawangyz0513@gmail.commwang@gps.gov.cn Search for other works by this author on: GSW Google Scholar Zheng‐Kang Shen; Zheng‐Kang Shen cDepartment of Earth and Space Sciences, University of California, Los Angeles, Los Angeles, California 90095‐1567 U.S.A.zshen@ucla.eduzhengkangshen@pku.edu.cn Search for other works by this author on: GSW Google Scholar Yongge Wan Yongge Wan dInstitute of Disaster Prevention Science and Technology, Yanjiao, Sanhe City, Hebei Province 065201, Chinawanyg217217@vip.sina.com Search for other works by this author on: GSW Google Scholar Author and Article Information Yanzhao Wang aState Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, Chinawangyz0513@gmail.commwang@gps.gov.cn Fan Wang bNational Geomatics Center of China, Beijing 100830, Chinawangfan0003@gmail.com Min Wang aState Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, Chinawangyz0513@gmail.commwang@gps.gov.cn Zheng‐Kang Shen cDepartment of Earth and Space Sciences, University of California, Los Angeles, Los Angeles, California 90095‐1567 U.S.A.zshen@ucla.eduzhengkangshen@pku.edu.cn Yongge Wan dInstitute of Disaster Prevention Science and Technology, Yanjiao, Sanhe City, Hebei Province 065201, Chinawanyg217217@vip.sina.com Publisher: Seismological Society of America First Online: 14 Jul 2017 Online ISSN: 1938-2057 Print ISSN: 0895-0695 © 2014 by the Seismological Society of America Seismological Research Letters (2014) 85 (1): 52–59. https://doi.org/10.1785/0220130111 Article history First Online: 14 Jul 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Yanzhao Wang, Fan Wang, Min Wang, Zheng‐Kang Shen, Yongge Wan; Coulomb Stress Change and Evolution Induced by the 2008 Wenchuan Earthquake and its Delayed Triggering of the 2013 Mw 6.6 Lushan Earthquake. Seismological Research Letters 2014;; 85 (1): 52–59. doi: https://doi.org/10.1785/0220130111 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySeismological Research Letters Search Advanced Search Almost five years after the 12 May 2008 Mw 7.9 Wenchuan earthquake, the Longmenshan fault zone was struck by the April 20 Mw 6.6 Lushan earthquake, with its hypocenter located ∼45 km southwest of the southern end of the Wenchuan surface rupture (Han et al., 2014; Zhang et al., 2014; Fig. 1). Such proximity in space and time between the two events implies that the later event is an aftershock of the previous one, or in other words, the previous event played a more important role in the occurrence of the latter... You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

The 20 April 2013 Lushan earthquake occurred on the southern section of the Longmen Shan fault system. Using GPS data from 33 continuous stations, we derive a three‐dimensional coseismic displacement field of the earthquake and invert for the location, geometry, and slip distribution of the fault rupture. Our study result indicates that the earthquake occurred on a reverse fault striking N28°E and dipping 43° to the NW, with the maximum slip located at 30.292°N, 102.943°E, and 13 km depth. The rupture is dominated by thrust faulting, with a slight but still statistically significant sinistral component. The seismic moment release is 9.5 × 1018 N · m, equivalent to a Mw6.6 earthquake. Our results suggest that at the southern end of the Longmen Shan fault zone near the triple junction with the Xianshuihe and Anninghe faults, the kinematic deformation field is no longer block‐like, but broadly distributed to accommodate the buttressing effect of deformation around the fault triple junction.

Magnetotelluric measurements were carried out along two profiles across the middle and southwestern sections of the Longmenshan fault zone (LMSf) from 2009 to 2011, after the 2008 Wenchuan M W7.9 earthquake. The former profile crosses the Wenchuan event epicenter and the latter one crosses 2013 Lushan M S7.0 event epicenter. The data were analyzed using advanced processing techniques, including phase tensor and two-dimensional inversion methods, in order to obtain reliable 2-D profiles of the electrical structure in the vicinity of the two earthquakes. A comparison of the two profiles indicates both similarities and differences in the deep crustal structure of the LMSf. West of the southwestern section, a crustal high conductivity layer (HCL) is present at about 10 km depth below the Songpan-Garzê block; this is about 10 km shallower than that under the middle section of the LMSf. A high resistivity body (HRB) is observed beneath the southwestern section, extending from the near surface to the top of upper mantle. It has a smaller size than the HRB observed below the middle section. In the middle section, there is a local area of decreased resistivity within the HRB but there is absence of this area. The 2013 Lushan earthquake occurred close to the eastern boundary of HRB and the Shuangshi-Dachuan fault, of which the seismogenic context has both common and different features in comparison with the 2008 Wenchuan event. On a large scale, the 2013 Lushan earthquake is associated with the HCL and deformation in the crust including HCL of the eastern Tibetan Plateau. In order to assess seismic risk, it is important to consider both the stress state and the detailed crustal structure in different parts of the LMSf.

As the southeastern margin of the Tibetan plateau,the Sichuan-Yunnan region is carved by ample tectonic active faults. Many strong earthquakes have taken place in the past,and some of which resulted in massive damages and great losses of human lives. In this study we attempt to estimate the seismic hazard potential using two different approaches. Our first approach follows Kagan and Jackson(1994)and uses earthquake catalog data to estimate the mid-to long-term spatial probability of strong earthquakes,based on the assumption that earthquake likelihood is proportional to the intensity and quantity of past events. A retrospective test shows that the model offers reasonable ‘forecasts'statistically over the last 37 years,based on the catalog data of previous 470 years for model constraints. Our second approach is to use secular geodetic strain rate deduced from GPS velocity data to constrain earthquake probability model,assuming that likelihood of strong earthquakes is spatially proportional to the geodetic strain rate. A retrospective test of the model with earthquake occurrence of the past 30 years shows that the model ‘forecasted’poorly,but did reasonably well when comparing with the catalog data of the past 500 years,suggesting that the geodetic strain rate obtained at the decade scale may still be a good indicator of long-term earthquake activity in the region,but only at a time scale of hundreds of years.

The 14 April 2010 Mw 6.9 Yushu earthquake ruptured the northwestern segment of the Ganzi-Yushu fault in Qinghai Province, China. Using GPS data obtained from 1999 to 2007 in the vicinity of the Ganzi-Yushu fault, we estimate the slip rates of the Fenghuoshan and Ganzi-Yushu faults, and the northwestern segment of the Xianshuihe fault as 6.1±1.9, 6.6±1.5, and 9.7±0.7mm/a for left lateral components, and 2.8±1.9, 1.7±1.6, and −2.0±0.9mm/a for shortening components, respectively. The Maduo-Gande fault slips left laterally at a rate of about 1–2mm/a, and ~3mm/a sinistral shear motion is left unexplained, possibly caused by deformation across one or more unknown faults in the region. These results agree with geological estimates of the fault slip rates, and show a progressive increase of shear motion from northwest to southeast across segments of the Xianshuihe–Ganzi-Yushu fault zone, implying variation in transferring and absorbing deformation in different regions in and around the Tibetan plateau.

The Longmenshan forms the eastern margin of the Tibetan Plateau adjacent to the Sichuan Basin. This range is anomalous because it formed despite low convergence and slip rates and without the development of a foreland basin. The devastating A.D. 2008 Wenchuan earthquake (Mw = 7.9) has renewed debate about the tectonics of the Longmenshan. A magnetotelluric (MT) study was undertaken subsequent to the earthquake to investigate the crustal structure of the Longmenshan, and inversion of the data reveals a low-resistivity (high-conductivity) layer at a depth of ∼20 km beneath the eastern Tibetan Plateau that terminates ∼25 km west of the Wenchuan-Maoxian fault. Its electrical properties are consistent with it being fluid-rich and mechanically weak. Beneath the Longmenshan and Sichuan Basin, a high-resistivity zone extends through the entire crust, but with a zone of low resistivity in the vicinity of the Wenchuan hypocenter. We show that the MT data, combined with other geological and geophysical observations, support geodynamic models for the uplift of eastern Tibet being caused by southeast-directed crustal flow that is blocked by stable lithosphere beneath the Sichuan Basin and Longmenshan, leading to inflation of the Songpan-Ganzi terrane. This rigid high-resistivity backstop not only provided a block to flow, but also may have accumulated stress prior to the earthquake. The MT observations provide new insights into the generation of the Wenchuan earthquake, which occurred in a region with low convergence rates prior to the earthquake.

Two days after the March 11, 2011, M w 9.0 Tohoku-oki earthquake, Shinmoedake volcano, located on the Japanese island of Honshu, erupted. Was this eruption triggered by the Tohoku-oki earthquake? Could Mount Fuji and Changbaishan volcanoes also be triggered to erupt? By calculating changes in the regional stress-strain field that resulted from the earthquake, we find that Mount Fuji, Shinmoedake and Changbaishan volcanoes are all located in regions of volumetric expansion. The volumetric expansions at a depth of 10 km are up to ∼220 nano-strain, ∼8 nano-strain, and ∼14 nano-strain, respectively, for the three volcanoes. The strain changes inferred from GPS co-seismic displacements also suggest that these three volcanoes are located in regions with surface areal expansion. Considering that the expansional stress may cause the opening of magma channels, exsolution of CO2 gases stored in magma, and a series of positive feedback effects, the Tohoku-oki earthquake may result in an increase in the activity of these volcanoes. Attention should be paid to potential triggering of volcanic eruptions by stress changes induced by the Tohoku-oki earthquake.

Analysis of GEONET observations covering the entire territory of Japan shows that the great Tohoku-oki earthquake that occurred on March 11, 2011 off the east coast of Honshu in Japan caused an eastward movement of the northern part of the island by as much as 5.3 m. The GPS data from TEONET in China were used to derive far-field coseismic displacements and to assess the impact of the Tohoku-oki earthquake on crustal deformation in eastern China. The results reveal that the coseismic horizontal displacements induced by the earthquake are the level of millimeters to centimeters in North and Northeast China, with a maximum of 35 mm. Strain analysis also indicates that the earthquake resulted in an increase in the tensile strain on the north-northeast trending faults in North and Northeast China. The tensile strain imposed on the Yilan-Yitong and Dunhua-Mishan faults is more significant than that imposed on the faults in North China; the maximum normal strain reaches about 40 nano-strain. Considering that the static Coulomb stress loaded on the faults is limited, its effect on the regional seismic activity may not be significant.

2008年3月21日新疆于田发生Ms7.3级地震.本文通过处理、分析GPS数据,得到破裂断层北侧100 km附近的同震位移及震后形变信息.在观测区域GPS点监测到10 mm左右的同震位移,其中最大为南向14 mm,东向5 mm.同震位移呈现一致性的东南向运动特征,证实于田地震存在显著的左旋走滑分量.震后台站向西南方向运动,与同震位移方向不同,说明同震位移和震后形变具有不同的形变源.近普鲁断裂两侧的GPS点震后运动方向存在明显差异,表明于田地震可能触发了普鲁断裂的左旋滑动.普鲁断裂在于田地震发生后呈现的构造活动特征揭示普鲁断裂是康西瓦—西阿尔金断裂带的一部分,兼具左旋走滑与逆冲分量,吸收了青藏高原西北缘相对于塔里木盆地的东向逃逸与北向入侵作用.

2011年3月11日日本宫城Mw9.0级大震后的两天九州岛上新燃岳火山发生大规模喷发.此次火山喷发是否是受地震触发所致,以及地震是否同样也会造成富士山火山和长白山火山的喷发成为人们关注的热点.通过对地震造成的区域应力应变场的计算,发现富士山火山、新燃岳火山和长白山火山均处于体膨胀区,在地下10km处体膨胀分别达到~220,~8和~14nano-strain.由同震GPS位移场计算得到的3个火山地区地表面应变也表现为膨胀,符合模型计算结果.考虑到拉张应力可能对岩浆通道产生的扩张作用、对包容在岩浆内二氧化碳气体的分异作用以及由此引发的一系列正反馈过程,此次地震可能造成这些火山活动的增加,应当警惕触发影响可能造成的火山喷发.

The 14 April 2010 MW 6.9 Yushu earthquake ruptured the northwestern segment of the Ganzi-Yushu Fault in Qinghai,China.Accurate estimation of the secular slip rate across the fault would help understand tectonic structure of the fault and its seismogenic process.GPS data obtained from 1999 to 2007around the Ganzi-Yushu Fault spanning 89°～103°E,28°～39°N make such estimation possible.After removing GPS stations whose displacements were affected by fault locking effects and/or deformation of other faults,we decompose the remaining GPS station velocities into strike-parallel and strike-normal components and examine the data along profiles across corresponding fault segments.The slip rates of the Fenghuoshan,Ganzi-Yushu,and northwestern segment of the Xianshuihe Faults are estimated as 6.1±1.9,6.6±1.5,and 10.2±0.7mm/a,respectively.These results agree with geological estimates of the fault slip rates,which show progressive increase from northwest to southeast across segments of the Ganzi-Yushu-Xianshuihe Fault zone,implying variation in transferring and absorbing patterns of deformation in different regions in and around the Tibetan plateau.Estimation of present-day slip rates along segments of the Ganzi-Yushu Fault would provide valuable data for future research on seismo-tectonics of the fault and tectonic evolution of the Tibetan plateau.

据覆盖日本全境的GEONET网络GPS观测资料显示,2011年3月11日的日本宫城MW9.0级地震造成日本半岛向东移动,最大达到了5.3m.利用国家重大科技基础设施项目"中国大陆构造环境监测网络"的GPS观测资料,分析此次地震对中国大陆构造形变场的同震影响,结果显示,地震造成我国东北和华北地区产生毫米至厘米级的同震水平位移,最大值为35mm.通过应变分析发现,地震导致东北和华北地区一系列北北东走向的断裂产生了不同程度的张性应变.虽然在东北地区张性应变相对比较明显,最大处约为40nano-strain,但对断裂带的静态库仑应力加载有限,不会对区域地震活动产生大的影响.