首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 921 毫秒
1.
The M w 8.6 Indian Ocean earthquake occurred on April 11, 2012 near the NW junction of three plates viz. Indian, Australian and Sunda plate, which caused widespread coseismic displacements and Coulomb stress changes. We analyzed the GPS data from three IGS sites PBRI, NTUS & COCO and computed the coseismic horizontal displacements. In order to have in-depth understanding of the physics of earthquake processes and probabilistic hazard, we estimated the coseismic displacements and associated Coulomb stress changes from two rectangular parallel fault geometries, constrained by Global Positioning System (GPS) derived coseismic displacements. The Coulomb stress changes following the earthquake found to be in the range of 5 to ?4 bar with maximum displacement of ～11 m near the epicenter. We find that most of the aftershocks occurred in the areas of increased Coulomb stress and concentrated in three clusters. The temporal variation of the aftershocks, not conformed to modified Omori’s law, speculating poroelastic processes. It is also ascertained that the spatio-temporal transient stress changes may promote the occurrence of the subsequent earthquakes and enhance the seismic risk in the region.  相似文献   

2.
In the southern South–North Seismic Zone, China, seismic activity in the Yingjiang area of western Yunnan increased from December 2010, and eventually a destructive earthquake of Ms5.9 occurred near Yingjiang town on 10 March 2011. The focal mechanism and hypocenter location of the mainshock suggest that the Dayingjiang Fault was the site of the mainshock rupture. However, most of foreshocks and all aftershocks recorded by a portable seismic array located close to the mainshock occurred along the N–S-striking Sudian Fault, indicating that this fault had an important influence on these shocks. Coulomb stress calculations show that three strong(magnitude ≥5.0) earthquakes that occurred in the study region in 2008 increased the coulomb stress along the plane parallel to the Dayingjiang Fault. This supports the Dayingjiang Fault, and not the Sudian Fault, as the seismogenic fault of the 2011 Ms5.9 Yingjiang earthquake. The strong earthquakes in 2008 also increased the Coulomb stress at depths of ≤5 km along the entire Sudian Fault, and by doing so increased the shallow seismic activity along the fault. This explains why the foreshocks and aftershocks of the 2011 Yingjiang earthquake were located mostly on the Sudian Fault where it cuts the shallow crust. The earthquakes at the intersection of the Sudian and Dayingjiang faults are distributed mainly along a belt that dips to the southeast at ~40°, suggesting that the Dayingjiang Fault in the mainshock area also dips to the southeast at ~40°.  相似文献   

3.
基于青藏高原及邻区的三维粘弹性有限元模型,讨论2008年于田MS7.3级地震与2014年于田MS7.3级地震之间的关系,并研究2014年于田MS7.3级地震的发生造成周围断层的库仑破裂应力变化。初步结果表明:1)2008年于田MS7.3级地震在2014年于田MS7.3级地震震中滑动方向上产生的库仑破裂应力变化高于地震触发的阈值0.01 MPa,存在明显的触发作用。在视摩擦系数分别取0.4和0.6时,震源区同震库仑破裂应力变化为0.0167 MPa和0.0170 MPa;而考虑粘弹性松弛作用时产生的库仑应力增加量分别为0.0187 MPa和0.0194 MPa。结合断裂带构造应力年累计速率的结果,2008年于田地震的发生造成2014年于田地震提前21.4~24.9 a;2)在较短的时间尺度内,对于距离相近的两次地震之间,同震产生的应力变化远大于粘弹性松弛效应产生的变化;3)2014年于田MS7.3级地震的发生造成阿尔金断裂中北段、玛尼—玉树断裂中段、东昆仑断裂西段、柴达木北缘断裂东段、西秦岭北缘断裂西段等不同程度的加载效应,地震危险性有所增强。其中阿尔金断裂中段库仑应力增加最为明显,最大达2.8×10–3 MPa;玛尼—玉树断裂中段次之,应力增加量最大达5.6×10–4 MPa;东昆仑断裂西段应力增加量最大达4.75×10–4 MPa。而玛尼—玉树断裂西段库仑破裂应力最大卸载量达3.6×10–3 MPa。  相似文献   

4.
We analyzed small repeating earthquakes recorded over a 13-year period and GPS data recorded over an 8-month period to estimate interplate quasi-static slip associated with the 2003 Tokachi-oki earthquake (M8.0) and the 2004 off-Kushiro earthquake (M7.1). The repeating-earthquake analysis revealed that the slip rate near the source region of the Tokachi-oki earthquake was relatively low (< 5 cm/year) prior to the earthquake; however, in the last 3 years leading up to the event, a minor acceleration in slip occurred upon the deeper extension of the coseismic slip area of the earthquake. Repeating-earthquake and GPS data indicate that large amounts of afterslip occurred around the rupture area following the earthquake; the afterslip mainly propagated to the east of the coseismic slip area. We also infer that the occurrence of the 2004 off-Kushiro earthquake, located about 100 km northeast of the epicenter of the Tokachi-oki earthquake, was advanced by the afterslip associated with the Tokachi-oki earthquake.  相似文献   

5.
Deformation models used to explain the triggering mechanism often assume pure elastic behaviour for the crust and upper mantle. In reality however, the mantle and possibly the lower crust behave viscoelastically, particularly over longer time scales. Consequently, the stress field of an earthquake is in general time-dependent. In addition, if the elastic stress increase were enough to trigger a later earthquake, this triggered event should occur instantaneously and not many years after the triggering event. Hence, it is appropriate to include inelastic behaviour when analysing stress transfer and earthquake interaction.In this work, we analyse a sequence of 10 magnitude Ms > 6.5 events along the North Anatolian Fault between 1939 and 1999 to study the evolution of the regional Coulomb stress field. We investigate the triggering of these events by stress transfer, taking viscoelastic relaxation into account. We evaluate the contribution of elastic stress changes, of post-seismic viscoelastic relaxation in the lower crust and mantle, and of steady tectonic loading to the total Coulomb stress field. We analyse the evolution of stress in the region under study, as well as on the rupture surfaces of the considered events and their epicentres. We study the state of the Coulomb stress field before the 1999 İzmit and Düzce earthquakes, as well as in the Marmara Sea region.In general, the Coulomb stress failure criterion offers a plausible explanation for the location of these events. However, we show that using a purely elastic model disregards an important part of the actual stress increase/decrease. In several cases, post-seismic relaxation effects are important and greater in magnitude than the stress changes due to steady tectonic loading. Consequently, viscoelastic relaxation should be considered in any study dealing with Coulomb stress changes.According to our study, and assuming that an important part of the rupture surface must be stressed for an earthquake to occur, the most likely value for the viscosity of the lower crust or mantle in this region is 5 · 1017–1018 Pa · s. Our results cannot rule out the possibility of other time-dependent processes involved in the triggering of the 1999 Düzce event. However, the stress increase due to viscoelastic relaxation brought 22% of the 1999 Düzce rupture area over the threshold value of Δσc ≥ 0.01 MPa (0.1 bar), and took the whole surface closer to failure by an average of 0.2 MPa. Finally, we argue that the Marmara Sea region is currently being loaded with positive Coulomb stresses at a much faster rate than would arise exclusively from steady tectonic loading on the North Anatolian Fault.  相似文献   

6.
The Killari earthquake of September 29, 1993 (Mw=6.2) in peninsular India triggered several aftershocks that were recorded by a network of 21 stations. We computed the change in regional static stress caused by coseismic slip on the earthquake rupture and correlated it with the aftershocks with a view to constrain some of the rupture parameters of this earthquake. We evaluated the six available estimates of fault plane solutions for this earthquake and concluded that reverse slip on a 42° dipping, N112° trending fault, which extends up to the surface from a depth of 7 km, produces maximum correlation between the increased static stress and aftershock distribution. Our analysis suggests that the majority of coseismic slip occurred on the part of the rupture that lies in the depth range of 3–6.5 km.  相似文献   

7.
The 10 June 2012 Mw 6.0 aftershock sequence in southwestern Anatolia is examined. Centroid moment tensors for 23 earthquakes with moment magnitudes (Mw) between 3.7 and 6.0 are determined by applying a waveform inversion method. The mainshock is a shallow focus strike-slip with reverse component event at a depth of 30 km. The seismic moment (Mo) of the mainshock is estimated as 1.28 × 1018 Nm and rupture duration of the Fethiye mainshock is 38 s. The focal mechanisms of the aftershocks are mainly strike-slip faulting with a reverse component. The geometry of the focal mechanisms reveals a strike-slip faulting regime with NE–SW trending direction of T-axis in the entire activated region. A stress tensor inversion of focal mechanism data is performed to obtain a more accurate picture of the Fethiye earthquake stress field. The stress tensor inversion results indicate a predominant strike-slip stress regime with a NW–SE oriented maximum horizontal compressive stress (SH). According to variance of the stress tensor inversion, to first order, the Fethiye earthquake area is characterized by a homogeneous interplate stress field. The Coulomb stress change associated with the mainshock and the largest aftershock are also investigated to evaluate any significant enhancement of stresses along the Gulf of Fethiye and surrounding region. Positive lobes with stress more than 0.4 bars are obtained, indicating that these values are large enough to increase the Coulomb stress failure towards NNW–SSE and E–W directions.  相似文献   

8.
李平恩  廖力  奉建州 《地球科学》2022,47(6):2149-2164
2019年6月17日四川长宁县发生6.0级地震,该次地震余震活动频度高、强度大,其中超过5.0级的强余震就有4次,具有不同于以往6.0级地震的独特特征.余震活动与震后区域应力变化密切相关,为研究它们之间的关系,考虑区域主要活动构造、地表起伏和深部反演结果,建立长宁地区岩石圈三维黏弹性有限元模型.采用数值方法重建基本符合研究区GPS观测和最大水平主压应力方向测量结果的现今构造背景应力场.进而依次模拟了长宁6.0级地震和5.0级以上强余震序列.通过计算库仑破裂应力变化研究了震后应力演化与余震分布,以及主震和5.0级强余震序列之间的关系.研究表明,长宁6.0级地震的发生可能与区域内非构造加载因素有关,余震活动明显受震后区域应力变化的控制.长宁地震后,于滩-长宁背斜在10 km深度应力得到充分释放,库仑破裂应力明显减小;而在3 km深度库仑破裂应力明显增加,应力水平仍然较高.   相似文献   

9.
We investigate spatial clustering of 2414 aftershocks along the Izmit Mw = 7.4 August 17, 1999 earthquake rupture zone. 25 days prior to the Düzce earthquake Mw = 7.2 (November 12, 1999), we analyze two spatial clusters, namely Sakarya (SC) and Karadere–Düzce (KDC). We determine the earthquake frequency–magnitude distribution (b-value) for both clusters. We find two high b-value zones in SC and one high b-value zone in KDC which are in agreement with large coseismic surface displacements along the Izmit rupture. The b-values are significantly lower at the eastern end of the Izmit rupture where the Düzce mainshock occurred. These low b-values at depth are correlated with low postseismic slip rate and positive Coloumb stress change along KDC. Since low b-values are hypothesized with high stress levels, we propose that at the depth of the Düzce hypocenter (12.5 km), earthquakes are triggered at higher stresses compared to shallower crustal earthquake. The decrease in b-value from the Karadere segment towards the Düzce Basin supports this low b-value high stress hypothesis at the eastern end of the Izmit rupture. Consequently, we detect three asperity regions which are correlated with high b-value zones along the Izmit rupture. According to aftershock distribution the half of the Düzce fault segment was active before the 12 November 1999 Düzce mainshock. This part is correlated with low b-values which mean high stress concentration in the Düzce Basin. This high density aftershock activity presumably helped to trigger the Düzce event (Mw = 7.2) after the Izmit Mw 7.4 mainshock.  相似文献   

10.
At the 2003 Tokachi-oki earthquake of M8, seafloor phenomena such as a generation process of tsunami, seafloor uplifts, turbidity current, etc., were observed using a cabled observatory installed on the seafloor. The turbidity current was observed as a benthic storm caused presumably by the mainshock. The seafloor uplifts were observed at the mainshock and continuously after the mainshock. The uplifts were 0.35, 0.37, and 0.12 m for epicentral distances of 25.5, 31.4, and 81.7 km, respectively. After the mainshock, a continuous uplift of the seafloor is observed at all three pressure gauge locations indicating that there was a change in the state of friction on the plate boundary interface by the mainshock. In this paper, we first show what was observed using the cabled observatory installed right above the focal area of the earthquake, and then we discuss to summarize these phenomena associated with the earthquake, its possible causes, and future directions in long term monitoring of seismogenic processes.  相似文献   

11.
The 12 September 2007 great Bengkulu earthquake (M w 8.4) occurred on the west coast of Sumatra about 130 km SW of Bengkulu. The earthquake was followed by two strong aftershocks of M w 7.9 and 7.0. We estimate coseismic offsets due to the mainshock, derived from near-field Global Positioning System (GPS) measurements from nine continuous SuGAr sites operated by the California Institute of Technology (Caltech) group. Using a forward modelling approach, we estimated slip distribution on the causative rupture of the 2007 Bengkulu earthquake and found two patches of large slip, one located north of the mainshock epicenter and the other, under the Pagai Islands. Both patches of large slip on the rupture occurred under the island belt and shallow water. Thus, despite its great magnitude, this earthquake did not generate a major tsunami. Further, we suggest that the occurrence of great earthquakes in the subduction zone on either side of the Siberut Island region, might have led to the increase in static stress in the region, where the last great earthquake occurred in 1797 and where there is evidence of strain accumulation.  相似文献   

12.
Two and a half years prior to China’s M7.9 Wenchuan earthquake of May 2008, at least 300 million metric tons of water accumulated with additional seasonal water level changes in the Minjiang River Valley at the eastern margin of the Longmen Shan. This article shows that static surface loading in the Zipingpu water reservoir induced Coulomb failure stresses on the nearby Beichuan thrust fault system at <17 km depth. Triggering stresses exceeded levels of daily lunar and solar tides and perturbed a fault area measuring 416 ± 96 km2. These stress perturbations, in turn, likely advanced the clock of the mainshock and directed the initial rupture propagation upward towards the reservoir on the "Coulomb-like" Beichuan fault with rate- and state-dependent frictional behavior. Static triggering perturbations produced up to 60 years (0.6%) of equivalent tectonic loading, and show strong correlations to the coseismic slip. Moreover, correlations between clock advancement and coseismic slip, observed during the mainshock beneath the reservoir, are strongest for a longer seismic cycle (10kyr) of M > 7 earthquakes. Finally, the daily event rate of the micro-seismicity (M ≥ 0.5) correlates well with the static stress perturbations, indicating destabilization.  相似文献   

13.
以山东郯城1668年大地震为例,以前人地表地质调查结果为约束,利用弹性位错理论初步获取了该地震的同震破裂模型;在此基础上,基于粘弹性分层模型分析了该地震的同震和震后形变,同时以主震断层为接收断层计算了库仑应力分布,进一步讨论了地幔不同粘滞性系数对地表形变和库仑应力变化的影响。计算结果显示,该地震是一个右旋走滑为主兼有一定逆冲性质的地震,其同震位移巨大,能量释放较彻底;同震破裂造成震中郯城县西北、东北和南部部分断层库仑应力增加,而震后形变使得这些断层库仑应力进一步增加,在单县、宿迁和日照等地,地震后350 a库仑应力变化量达到+1bar-+1MPa量级;地幔粘滞性系数不同,形变量和库仑应力变化达到稳定的时间不同,但最终趋于稳定的数值基本一致。  相似文献   

14.
Eyidogan  Nalbant  Barka  & King 《地学学报》1999,11(1):38-44
The 1924 Pasinler & 1983 Horasan-Narman earthquakes which struck the Erzurum region occurred on the NE–SW-trending Horasan fault zone about 60 km east of Erzurum basin. The inversion of teleseismic seismograms, the aftershock pattern and the surface faulting of the 30 October 1983 ( M s = 6.8) Horasan-Narman earthquake indicate that it had dominantly left-lateral motion. One moderately sized aftershock occurred 8 h after the main event and two others a year later on the NE extension of the fault zone. The aftershock distribution dominantly overlapped with the Horasan fault zone, and the aftershocks also migrated from south-west to north-east within the year following the mainshock. The results obtained from modelling of static stress changes caused by the 1983 earthquake are consistent with the spatial distribution of aftershocks. Macroseismic observations of the 1924 earthquake ( M s = 6.8) indicated that this event occurred on the SW extension of the Horasan fault zone. Static stress modelling of the 1924 earthquake, by using the same input parameters of the 1983 event, has shown that its occurrence increased the stress in the region of the 1983 rupture zone. The static stress changes caused both by the 1924 and the 1983 earthquakes has increased the failure stress at the NE and SW extensions of the Horasan fault zone and in Narman area. Furthermore, the stress has decreased in the vicinity of the Erzurum fault zone, east of the city of Erzurum, the largest city in eastern Turkey, and in the populated Sarikamis area. This might delay the occurrence of a future probable damaging earthquake in these areas.  相似文献   

15.
We have computed static stress changes associated to several earthquakes occurred in the Apennine chain, in Italy. Stress associated with fault slip has been computed by the Okada (1992) formulation. Static Coulomb stress changes associated to three subevents forming the Irpinia, 1980, Ms=6.9 main shock indicate that such subevents have been consecutively triggered, each one by stress changes produced by previous ones. Furthermore, aftershocks of this complex faulting event are well correlated with zones of maximum increase of Coulomb stress. The interplay of regional stress and of local stress changes due to the mainshock produces an aftershock distribution considerably wide and a large variability of focal mechanisms. Variability of focal mechanism is consistent with a low level of background regional stress (less than 2 Mpa). The analysis of two further seismic sequence in the central Apennine, occurred on 1979 close to Norcia town (ML=5.9) and on 1984 in National Park of Abruzzo (ML=5.5), also show a clear correlation of aftershock occurrence with positive Coulomb stress changes generated by mainshocks. The static stress change due to the mainshock of 1984, in Abruzzo region, is likely to have triggered, 4 days after, a further mainshock (ML=5.1) on the northern edge prolongation of the main fault, where the Coulomb stress change is maximum.Such evidences indicate a strong correlation among earthquakes in the Apennine chain, trough static stress changes, at several time and space scales. Modelling of such effects is useful both for improving our knowledge of the earthquake dynamics and for a better evaluation of seismic hazard in Italy.  相似文献   

16.
P. Mandal  S. Horton   《Tectonophysics》2007,429(1-2):61-78
The HYPODD relocation of 1172 aftershocks, recorded on 8–17 three-component digital seismographs, delineate a distinct south dipping E–W trending aftershock zone extending up to 35 km depth, which involves a crustal volume of 40 km × 60 km × 35 km. The relocated focal depths delineate the presence of three fault segments and variation in the brittle–ductile transition depths amongst the individual faults as the earthquake foci in the both western and eastern ends are confined up to 28 km depth whilst in the central aftershock zone they are limited up to 35 km depth. The FPFIT focal mechanism solutions of 444 aftershocks (using 8–12 first motions) suggest that the focal mechanisms ranged between pure reverse and pure strike slip except some pure dip slip solutions. Stress inversion performed using the P and T axes of the selected focal mechanisms reveals an N181°E oriented maximum principal stress with a very shallow dip (= 14°). The stress inversions of different depth bins of the P and T axes of selected aftershocks suggest a heterogeneous stress regime at 0–30 km depth range with a dominant consistent N–S orientation of the P-axes over the aftershock zone, which could be attributed to the existence of varied nature and orientation of fractures and faults as revealed by the relocated aftershocks.  相似文献   

17.
玉树地震序列重新定位及其地震构造研究   总被引：3，自引：0，他引：3  
对玉树地震序列自2010年4月11日至9月15日由台网记录到的1 832个地震采用双差地震定位法进行重新定位,获得了1 670个地震重新定位的震源参数。重新定位后的震源深度主要分布在15 km以内。重新定位后的Ms 7.1级主震发生在无地表破裂段,余震活动向两侧破裂扩展。余震沿地表破裂带基本呈线性分布,剖面上显示为近垂直的结构面,在北西端无地表破裂出露处,出现近垂直于断裂方向较宽的北东向地震密集带。震源机制解显示的主压应力方向斜交地表破裂带,地表破裂与震源破裂都表现为纯左旋走滑的错动性质,而在北西端主压应力方向偏转为近垂直于断裂带的方向,此处较宽的北东向地震密集带可能由近东西与南北两个方向的共轭破裂所组成。余震的后期活动与发展并不局限于主震形成的破裂带内,更多的受局部应力调整被触发而产生新的破裂。  相似文献   

18.
汶川"5.12"8.0级特大地震,造成重大人员伤亡和财产损失。地震对周围地区断层活动性的影响和余震发展方向是人们关心的一个问题。根据汶川地震同震静态位移我们计算了周围地区一些断层的库仑应力变化,并据此评价了震后周围地区断层和地震的活动性。计算结果表明,龙门山断裂带东北段,包括北川、青川、宁强等地,为库仑应力增强区,有利于地震的发生。较大的余震分布与库仑应力增强区有较好的对应关系。鲜水河断裂带主要为库仑应力下降区,只有一小段为增高区,鲜水河断裂带总体上不利于地震活动。成都地区的西北部库仑应力增强,东南部应力下降。库仑应力变化的研究对大震后地震趋势的分析有重要意义。  相似文献   

19.
The evidence of coseismic uplift on the dynamic, wave-dominated Hua-tung coast fringing the active Coastal Range (eastern Taiwan) has been equivocal, due to complex controls by wave and terrestrial sediment over morphological and ecological systems of the coast. This study, by applying radiocarbon dating methods, demonstrates coseismic-uplift nature of the coast by finding synchronously killed intertidal organisms (mostly boring shell Jouannetia sp.) stranded at different sites of the coast with distinct physiographic characters. Based on these data, together with evidence from wave-cut notch sequences, two coseismic-uplift systems are recognized. One centers around the northern-middle part of the coast and yields events with uplift amounts of maximal 3–6 m and an average recurrence interval of at least several hundred years. The most recent activity of this system, influencing at least 70 km of coast, occurred at ~ 0.9 ka. The earthquake generating this event also triggered extensive landslides/debris flows in the region. Another system, exemplified by the uplift associated with the 2003 Cheng-kung earthquake, centers on the southern part of the coast and yields uplift of likely < 1 m every < 0.2 ky. Two pre-historic events of this system are identified as occurring at ~ 0.7 ka and ~ 1.1 ka. These two coseismic-uplift systems are consistent in position with two anticlinal structures defined by long-term uplift of the coast. However, the areas subjected to maximal coseismic uplift are located off where the climaxes of long-term uplift occur, implying that the latter areas have been uplifted mainly by aseismic and/or relatively frequent/small-magnitude coseismic motion.  相似文献   

20.
We observe the spatial distributions of the magnitude of aftershocks following the six earthquakes of focal depth shallower than 20 km with magnitude more than 5.0 from 1983 to 1987 in Japan. The upper limit of the aftershock magnitude is examined as a function of the distance from mainshock hypocentre. The observed spatial distributions of the upper limit are bimodal, with a tendency of the upper limit to decrease as the distance from mainshock hypocentre increases. Moreover, we observe the correlations between the aftershock spatial distribution and earthquake fault length. We focus on the largest aftershocks in each of two aftershock sequences constituting the bimodal distribution. The distances of the two largest aftershocks from the mainshock hypocentre are equal to the fault lengths of shallow earthquakes in Japan and to the maximum earthquake fault lengths.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号