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1.
V. O. Mikhailov I. Panet M. Hayn E. P. Timoshkina S. Bonvalot V. Lyakhovsky M. Diament O. de Viron 《Izvestiya Physics of the Solid Earth》2014,50(2):177-191
Comparative analysis of coseismic and postseismic variations of the Earth’s gravity field is carried for the regions of three giant earthquakes (Andaman-Sumatra, December 26, 2004, magnitude M w = 9.1; Maule-Chile, February 27, 2010, M w = 8.8, and Tohoku-Oki, March 11, 2011, M w = 9.0) with the use of GRACE satellite data. Within the resolution of GRACE models, the coseismic changes of gravity caused by these seismic events manifest themselves by large negative anomalies located in the rear of the subduction zone. The real data are compared with the synthetic anomalies calculated from the rupture surface models based on different kinds of ground measurements. It is shown that the difference between the gravity anomalies corresponding to different rupture surface models exceeds the uncertainties of the GRACE data. There-fore, the coseismic gravity anomalies are at least suitable for rejecting part of the models that are equivalent in the ground data. Within the first few months after the Andaman-Sumatra earthquake, a positive gravity anomaly started to grow above the deep trench. This anomaly rapidly captured the area of the back-arc basin and largely compensated the negative coseismic anomaly. The processes of viscoelastic stress relaxation do not fully allow for these rapid changes of gravity. According to the calculations, even with a sufficiently low viscosity of the upper mantle, relaxation only covers about a half of the observed change of the field. In order to explain the remaining temporal variations, we suggested the process of downdip propagation of the coseismic rupture surface. The feasibility of such a process was supported by numerical simulations. The sum of the gravity anomalies caused by this process and the anomaly generated by the processes of viscoelastic relaxation accounts well for the observed changes of the gravity field in the region of the earthquake. The similar postseismic changes of gravity were also detected for the region of the Tohoku-Oki earthquake. Just as in the case discussed above, this earthquake was also followed by a rapid growth of a positive postseismic anomaly, which partially counterbalanced the negative coseismic anomaly. The time variations of the gravity field in the region of the Maule-Chile earthquake differ from the pattern of changes observed in the island arcs described above. The postseismic gravity variations are in this case concentrated in a narrower band above the deep trench and shelf, and they do not spread over the continental territory, where the negative coseismic anomaly is located. These discrepancies reflect the difference in the geodynamical settings of the studied earthquakes. 相似文献
2.
基于中国大陆1998～2007年（复测周期2～3年）流动重力观测数据,结合GPS、水准观测成果和区域地质构造动力环境,分析研究了汶川8.0级地震区域重力场动态变化演化特征和孕震机理.结果表明：区域重力场动态演化大体反映了青藏高原物质东流的动态效应和汶川大震孕育的中长期（2～10年）信息;汶川大震孕育的显著重力标志为震中西南持续多年的正重力变化（上升）和出现较大规模的重力变化梯级带,前者有利于地震能量的不断积累,后者有利于地震剪切破裂的发生;与地震孕育相关重力场变化总体呈增大—加速增大—减速增大—发震的过程;8年累积重力变化幅差最大约200×10-8m·s-2;2001年昆仑山口8.1级地震孕育发生和震后恢复调整,对区域重力场动态变化和汶川大震的孕育发展具有重要影响;松潘—甘孜块体一般呈现负重力变化,可能反映深部壳幔局部上隆、壳内温度较高而膨胀,有利于逆冲或推覆体运动的形成和大震的发生. 相似文献
3.
本研究通过对重力卫星GRACE观测数据的处理,采用去相关加300 km半径的高斯平滑,成功地提取了2010智利Mw8.8地震所产生的重力变化信号,最大变化幅度达到7 μGal,并且与位错理论计算结果具有较好的一致性.这是继GRACE检测出2004苏门答腊M9.3地震重力变化后的又一个卫星观测地震的例证,说明GRACE具有检测出M<9.0量级地震的能力,为利用GRACE研究地震以及其更广泛的应用提供了可靠的依据. 相似文献
4.
本文在考虑全球陆面数据同化系统陆地水储量变化影响后,利用2002年4月—2015年4月GRACE卫星RL05月重力场模型获取了2011年日本MW9.0地震震中及其周边区域的重力场信息;然后给出了日本及其周边2003—2015年的年度累积重力变化和差分重力变化,并且利用经验正态函数方法深入分析了该地震过程中同震重力变化对区域重力场的贡献. 结果显示:日本MW9.0地震前研究区域出现了幅值高达2×10-8 m/s2的异常重力变化,其同震效应的时间和空间特征均出现在第一模态,且同震重力变化和震后区域重力场变化特征显著,这充分表明该地震对区域重力场的影响显著. 相似文献
5.
本文利用2003—2011年的GRACE RL05数据提取了苏门答腊地震(Mw9.3)引起的震后重力变化,发现断层两侧震后重力变化速率存在明显差异,断层下盘总体变化率为0.55μGal/yr,断层上盘为0.16μGal/yr.基于子断层叠加的编程思想,本文将Tanaka的黏弹球体位错理论配套计算程序(简称黏弹位错程序)加以改造,克服了其近场计算精度不足(甚至错误)的缺陷,可用来研究大地震引起的近场震后位移与重力变化.本文利用改造后的黏弹位错程序计算了2004年苏门答腊地震(Mw9.3)产生的同震重力变化,计算结果在空间分布和量级上均与利用弹性位错程序计算获得的结果一致,验证了我们对黏弹位错程序进行改造的正确性.最后,结合GRACE卫星观测数据,本文利用Tanaka的黏弹位错理论研究了苏门答腊地区的地幔黏性因子.结果表明,该地区地幔黏滞性具有显著的横向差异,当发震断层上下两盘的地幔黏滞性系数分别取8×1018 Pa·s和1×1018 Pa·s时,模拟的震后重力变化在总体空间分布和变化趋势上与GRACE卫星观测结果更接近. 相似文献
6.
V. O. Mikhailov M. Diament A. A. Lyubushin E. P. Timoshkina S. A. Khairetdinov 《Izvestiya Physics of the Solid Earth》2016,52(5):692-703
The refinement of the accuracy and resolution of the monthly global gravity field models from the GRACE satellite mission, together with the accumulation of more than a decade-long series of these models, enabled us to reveal the processes that occur in the regions of large (Mw≥8) earthquakes that have not been studied previously. The previous research into the time variations of the gravity field in the regions of the giant earthquakes, such as the seismic catastrophes in Sumatra (2004) and Chile (2010), and the Tohoku mega earthquake in Japan (2011), covered the coseismic gravity jump followed by the long postseismic changes reaching almost the same amplitude. The coseismic gravity jumps resulting from the lower-magnitude events are almost unnoticeable. However, we have established a long steady growth of gravity anomalies after a number of such earthquakes. For instance, in the regions of the subduction earthquakes, the growth of the positive gravity anomaly above the oceanic trench was revealed after two events with magnitudes Mw=8.5 in the Sumatra region (the Nias earthquake of March 2005 and the Bengkulu event of September 2007 near the southern termination of Sumatra Island), after the earthquake with Mw=8.5 on Hokkaido in September 2007, a doublet Simushir earthquake with the magnitudes Mw = 8.3 and 8.1 in the Kuriles in November 2006 and January 2007, and after the earthquake off the Samoa Island in September 2009 (Mw=8.1). The steady changes in the gravity field have also been recorded after the earthquake in the Sichuan region (May 2008, Mw = 8.0) and after the doublet event with magnitudes 8.6 and 8.2, which occurred in the Wharton Basin of the Indian Ocean on April 11, 2012. The detailed analysis of the growth of the positive anomaly in gravity after the Simushir earthquake of November 2006 is presented. The growth started a few months after the event synchronously with the seismic activation on the downdip extension of the coseismically ruptured fault plane zone. The data demonstrating the increasing depth of the aftershocks since March 2007 and the approximately simultaneous change in the direction and average velocity of the horizontal surface displacements at the sites of the regional GPS network indicate that this earthquake induced postseismic displacements in a huge area extending to depths below 100 km. The total displacement since the beginning of the growth of the gravity anomaly up to July 2012 is estimated at 3.0 m in the upper part of the plate’s contact and 1.5 m in the lower part up to a depth of 100 km. With allowance for the size of the region captured by the deformations, the released total energy is equivalent to the earthquake with the magnitude Mw = 8.5. In our opinion, the growth of the gravity anomaly in these regions indicates a large-scale aseismic creep over the areas much more extensive than the source zone of the earthquake. These processes have not been previously revealed by the ground-based techniques. Hence, the time series of the GRACE gravity models are an important source of the new data about the locations and evolution of the locked segments of the subduction zones and their seismic potential. 相似文献
7.
ＴｈｅｍｅｃｈａｎｉｓｍｏｆｒｅｇｉｏｎａｌｇｒａｖｉｔｙｃｈａｎｇｅｓｂｅｆｏｒｅａｎｄａｆｔｅｒｔｈｅＴａｎｇｓｈａｎｅａｒｔｈｑｕａｋｅＲＵＩ－ＨＡＯＬＩ（李瑞浩）ＪＩＡＮ－ＬＩＡＮＧＨＵＡＮＧ（黄建梁）ＨＵＩＬＩ（李辉）ＤＯＮＧ－ＳＨＥＮＧ... 相似文献
8.
Jin-Zhao Liu Tong-Qing Wang Zhao-Hui Chen Pin Zhang Chuan-Dong Zhu Shuang-Xi Zhang 《应用地球物理》2018,15(1):137-146
We evaluated 2011–2015 mobile relative gravity data from the Hexi monitoring network that covers the epicenter of the 2016 Menyuan Ms6.4 earthquake, Qinghai Province, China and examined the spatiotemporal characteristics of the gravity field at the focal depth. In addition, we assessed the regional gravity field and its variation the half-year before the earthquake. We use first different interpolation algorithms to build a grid for the gravity data and then introduce potential field interpolation–cutting separation techniques and adaptive noise filtering. The results suggest that the gravity filed at the focal depth of 11.12 km separated from the total gravity field at about–400~150 × 10?8 m/s2 in the second half of 2015, which is larger than that in the same period in 2011 to 2014 (±30 × 10?8 m/s2). Moreover, at the same time, the gravity field changed fast from September 2014 to May 2015 and May 2015 to September 2015, reflecting to some extent material migration deep in the crust before the Menyuan earthquake. 相似文献
9.
2021年5月21日晚21时48分,云南省大理州漾濞县(震中:25.67°N,99.87°E)发生M_S6.4地震,震源深度8 km。为快速获得此次地震同震形变场及断层几何参数,研究该次地震的发震构造等,文章基于震前、震后的sentinel-1A卫星升降轨SAR数据进行二轨法差分雷达干涉测量(DInSAR),并基于Okada弹性半空间位错模型反演断层几何参数。研究结果如下:(1)此次地震造成的同震形变场长约19 km,宽约20 km;(2)升轨雷达视线向最大形变约为8.2 cm,降轨雷达视线向最大形变约为8.7 cm;(3)地震断层走向为313.7°,倾角为87°,滑动角为175°,为右旋走滑型断层,最大滑动量为0.79 m,反演得出的地震矩为1.48×10~(18) N·m,矩震级为M_W6.1。在川滇块体向南挤出的构造背景下,块体西边界的维西—乔后断裂、红河断裂发生右旋走滑,本次地震便是维西—乔后断裂南段分支断裂右旋走滑活动的体现。 相似文献
10.
利用GPS和GRACE观测数据研究了日本MW9.0地震的震后变形特征.GPS观测显示,区域震后位移呈现随指数函数变化特征,变化速率符合大森公式的衰减特性;近五年的震后水平位移累积已达到东向60~165 cm,南向20~65 cm的量值,距震中较远站点已超过同震变化量,且震后变形仍然持续.GRACE观测到显著的震后重力变化,地震破裂两侧的重力变化总体均呈上升趋势,但海洋侧的变化速率较快.联合震后余滑和黏弹性位错理论对震后变形进行了模拟,探索了GPS和GRACE观测的综合应用方法.研究发现,综合考虑震后余滑和黏滞性松弛效应可以对日本地震的震后变形做出较合理的解释,震后初期余滑起主要作用,1至2年以后逐渐减弱,黏滞性松弛作用逐渐增强.在震后变形模拟和区域黏滞性结构反演中形成GPS和GRACE观测结合应用的方法,先基于震后GPS形变估算区域黏滞性结构,而后利用GRACE观测修正深部的黏滞系数,并综合利用这两种观测微调浅层黏滞系数,最终确定区域黏滞性结构.基于该方法反演了日本震源区的地幔黏滞性结构,地震断层破裂两侧的流变参数存在差异,大陆侧的地幔顶层黏滞系数在1.0×1019 Pa·s量级,而海洋侧的则略小于大陆的,在6.0×1018 Pa·s量级. 相似文献
11.
由于GRACE Follow-On双星系统等效于基线长为星间距离的一维水平重力梯度仪,因此本文基于GRACE Follow-On卫星重力梯度法开展了精确和快速反演下一代地球重力场的可行性论证研究. 研究结果表明：第一,基于GRACE Follow-On卫星重力梯度法（GFO-SGGM）,利用卫星轨道参数（轨道高度250 km、星间距离50 km、轨道倾角89°、轨道离心率0.001）、关键载荷测量精度（星间距离10-6 m、星间速度10-7 m·s-1、星间加速度10-10 m·s-2、轨道位置10-3 m、轨道速度10-6 m·s-1、非保守力10-11 m·s-2）、观测时间30天和采样间隔10 s反演了120阶地球重力场,在120阶处累计大地水准面精度为9.331×10-4 m. 第二,在120阶内,利用将来GRACE Follow-On双星反演地球重力场精度较现有GRACE双星平均提高61倍,因此GRACE Follow-On卫星重力梯度法是进一步提高地球重力场反演精度的优选方法. 第三,下一代GRACE Follow-On计划较当前GRACE计划的优点如下：轨道高度更低（200~300 km）、载荷精度更高（10-7 ~10-9 m·s-1）和星间距离更短（50~100 km）. 相似文献
12.
运用升、降轨Sentinel-1A 卫星的差分干涉影像,获取2019-06-17四川宜宾长宁 MS6．0地震的三维同震形变场.在此基础上,以升降轨同震形变数据为约束条件,基于 Okada弹性半空间位错模型反演得到发震断层符合走滑和逆冲特征,断层破裂尺度约为15km×20km,断层滑动角为 44．37°,断层倾角为56．42°,震源深度约为10．2km,矩震级为 M W5．8.最后,采用SBAS-InSAR 技术获取该地区2019-04-05至2019-08-03各时间段的累计形变,结果认为该区域在震前近场形变波动较小,震后一段时间累积形变增长,分析原因可能是余震分布使得地表变化处于不稳定状态.通过与已有研究文献的比较和对该区域断层构造的分析,推测此次长宁地震发震断层由反演出的断层滑动引起,滑动面上缘接近地表,主震引起的次级断层活动触发短期内强余震频发. 相似文献
13.
The complete records of geoelectric resistivity before two earthquakes were analyzed, including 16 stations within 240 km
around the Tangshan earthquake and 2 stations within 50–60 km from theM6.1 Datong earthquake. By eliminating various disturbances in the records and realizing the precursory anomalies to be reliable,
the authors studied the distribution of the geoelectric precursor field, which proves to be physically related to the earthquake
source stress field. Comparision of the sign distribution of coseismic resistivity changes with the solution of earthquake
source mechanism indicates that, the coseismic resistivity changes are of opposite sign but similar spatial distribution with
respect to the corresponding resistivity precursor changes. Therefore, from the resistivity observations we are of the opinion
that the Tangshan earthquake is an elastic rebound process. A virtual dislocation model of geoelectric precursor for the Tangshan
earthquake is proposed, in which the geoelectric precursors are supposed to be caused by the strain accumulation due to a
virtual dislocation, which is opposite in sign to the actual slip taking place at the earthquake occurrence. Taking into account
of the non-linear characteristics of the amplification factorK=(Δρ/ρ)/ɛ in a range of 10−7–10−5 strain changes, the theoretical distribution of geoelectric precursors for the Tangshan earthquake was calculated based on
the theory of fracture mechanics and reasonably selected dislocation parameters. The results show that the semi-quantitative
theoretical values are in good agreement with the observed, suggesting that the virtual dislocation model of the geoelectric
precursor is appropriate to the Tangshan earthquake.
Contribution No. 96A0023, Institute of Geophysics, SSB, China.
This work was supported by the National Natural Science Foundation of China and the Science and Technology Department of SSB. 相似文献
14.
ＧｒａｖｉｔａｔｉｏｎａｌｅｆｆｅｃｔｏｆｗａｔｅｒｃｉｒｃｕｌａｔｉｏｎｉｎｔｈｅｎｏｒｔｈｗｅｓｔＹｕｎｎａｎＭｉｎ－ＹｕＪＩＡ；（贾民育）Ｓｈａｏ－ＡｎＳＵＮ；（孙少安）Ａｉ－ＭｉｎＸＩＡＮＧ；（项爱民）ａｎｄＤｏｎｇ－ＺｈｉＬＩＵ（刘冬至）（... 相似文献
15.
The Gravity Recovery and Climate Experiment (GRACE) has been measuring temporal and spatial variations of mass redistribution within the Earth system since 2002. As large earthquakes cause significant mass changes on and under the Earth’s surface, GRACE provides a new means from space to observe mass redistribution due to earthquake deformations. GRACE serves as a good complement to other earthquake measurements because of its extensive spatial coverage and being free from terrestrial restriction. During its over 10 years mission, GRACE has successfully detected seismic gravitational changes of several giant earthquakes, which include the 2004 Sumatra–Andaman earthquake, 2010 Maule (Chile) earthquake, and 2011 Tohoku-Oki (Japan) earthquake. In this review, we describe by examples how to process GRACE time-variable gravity data to retrieve seismic signals, and summarize the results of recent studies that apply GRACE observations to detect co- and post-seismic signals and constrain fault slip models and viscous lithospheric structures. We also discuss major problems and give an outlook in this field of GRACE application. 相似文献
16.
本文以龙门山及周边地区为研究对象,考虑区域地质构造差异、主要活动断裂带、地表附加重力影响,建立能反映地表起伏和岩石圈分层结构的龙门山地区三维粘弹性有限元模型。以地壳水平运动速率观测值为约束条件重建研究区现今构造背景应力场,在此基础上分别模拟了汶川地震和芦山地震的发生机理。通过分析同震库仑破裂应力变化与余震空间分布的关系,探讨了2次地震主震对余震的触发作用以及汶川地震对芦山地震的影响。研究表明,汶川地震和芦山地震的余震大部分由其主震触发,汶川地震对芦山地震的余震有约6.78%的触发作用。汶川地震的同震库仑破裂应力在芦山地震主震位置的增加值约为0.016MPa,如果龙门山断裂带南段库仑破裂应力年累积速率按照0.4×10-3-0.6×10-3MPa·a-1计算,汶川地震使芦山地震提前了约27-40年。计算还表明汶川地震和芦山地震的发生使鲜水河断裂带南段和虎牙断裂的库仑破裂应力增加,这些断裂带在未来发生地震的可能性增加。 相似文献
17.
利用GRACE卫星重力资料,计算了中国大陆及周边的卫星重力时变场和地表密度变化分布,获取了具有代表性的点位区域的每月重力变化时间序列.同时获得了WUSH、LHAS、KUNM、LUZH站相对于区域参考框架的GPS位移时间序列.卫星重力观测结果显示喜马拉雅弧形带的重力在2004年苏门答腊Mw9.3地震后快速下降, 2006~2008年尤为明显,西域地块西北边界带上震后重力下降也较为显著;而沿青藏高原北至东边界2007年出现明显的重力上升沿构造边界的弧形分布,且2008年南北地震带中南段重力上升变化显著.这些苏门答腊地震后的重力变化趋势到汶川地震发生后才开始改变.GPS位移结果显示四个台站均记录到苏门答腊大地震的同震信号,震后WUSH、LHAS、KUNM站水平位移向量出现明显的运动趋势改变,且一直持续到2008年汶川Ms8.0地震的发生.GRACE卫星揭示的青藏高原及周边地表质量的变化为解释汶川地震的动力机制提供了新的观测途径和资料.本文结合区域构造运动的特点和GPS位移,对GRACE观测的时变重力场特征及汶川地震的动力机制进行了初步解释和讨论. 相似文献
18.
自2002年以来,GRACE卫星探测计划可提供高精度的时变地球重力场,用以探测地球系统的物质分布.自1998年中国大陆重力监测网建立以来,利用FG5绝对重力仪和LCR-G型相对重力仪每2年对该网进行重复测量获取重力场时变信息.基于此,本文利用GRACE和地面重力测量获得了中国大陆重力场的长期年变率,利用位错理论根据USGS发布的断层模型计算了2008年汶川Ms8.0级地震的同震重力变化并进行了300 km高斯滤波.GRACE卫星重力和地面重力结果均表明华北地区地下水流失严重,在绝对重力基准站上,GRACE卫星重力与绝对重力变化率较为一致,汶川区域的地面重力变化结果可视为大地震前兆信息. 相似文献
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Long-period strain seismogram recorded at Pasadena is used to determine the focal process of the 1960 Chilean earthquake. Synthetic seismograms computed for various fault models are matched with the observed strain seismogram to determine the fault parameters. A low-angle (～ 10°) thrust model with rupture length of 800 km and rupture velocity of 3.5 km/sec is consistent with the observed Rayleigh/Love wave ratio and the radiation asymmetry. A seismic moment of 2.7 · 1030 dyn · cm is obtained for the main shock. This value, together with the estimated fault area of 1.6 · 105 km2, gives an average dislocation of 24 m. The strain seismogram clearly shows unusually long-period (300–600 sec) wave arriving at the P time of a large foreshock which occurred about 15 minutes before the main shock, suggesting a large slow deformation in the epicentral area prior to the major failure. A simple dislocation model shows that a dislocation of 30 m, having a time constant of 300–600 sec, over a fault plane of 800 × 200 km2 is required to explain this precursory displacement. The entire focal process may be envisaged in terms of a large-scale deformation which started rather gradually and eventually triggered the foreshocks and the “main” shock. This mechanism may explain the large premonitory deformations documented, but not recorded instrumentally, for several Japanese earthquakes. The moments of the main shock and the precursor add to 6 · 1030 dyn · cm which is large enough to affect the earth's polar motion. 相似文献
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为了解青藏高原东北缘岩石圈变形特征,进一步研究该地区地壳运动的壳-幔耦合机理,本文通过处理分析该地区1999～2007年多期GPS观测数据、1972~2000年水准测量数据和1992年及2007年相对重力测量资料,获得了该区域地壳水平运动速度场、较长时间段的垂直形变场和相对重力变化场.分析发现青藏高原东北缘东西部的变化特征存在明显差异：西部以北东向地壳缩短运动为主,而东部以顺时针旋转为主;东部以地壳隆升为主,速率在2.1 mm/a左右,而西部隆升的速率小于1 mm/a;相对重力变化则表现为在整体增大的背景下东部升高速率较大,平均为9.0×10-8 m·s-2·a-1,而西部较小,平均值为3.1×10-8 m·s-2·a-1.我们还发现,地壳不同变形形式的转换不是渐变的,而是发生在较窄的一个转换带内.这个转换带的整体走向为NEE,北部位于金昌与武威之间,中部在祁连山东部、门源以西,南部位于德令哈以东青海湖以西.最后结合前寒武纪构造格架、重力均衡异常资料和地震SKS分裂结果对形成这种运动态势的机理进行了探讨,我们认为岩石圈物质侧向流动、岩石圈结构及壳-幔耦合方式差异可能是导致东部与西部岩石圈变形差异主要动因. 相似文献