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1.
The moment tensor solution, source time function and spatial-temporal rupture process of the MS6.4 earthquake, which occurred in Ning’er, Yunnan Province, are obtained by inverting the broadband waveform data of 20 global stations. The inverted result shows that the scalar seismic moment is 5.51×1018 Nm, which corresponds to a moment magnitude of MW 6.4. The correspondent best double couple solution results in two nodal planes of strike 152°/dip 54°/rake 166°, and strike 250°/dip 79°/ rake 37°, respectively...  相似文献   

2.
At GMT time 13:19, August 8, 2017, an Ms7.0 earthquake struck the Jiuzhaigou region in Sichuan Province, China, causing severe damages and casualties. To investigate the source properties, seismogenic structures, and seismic hazards, we systematically analyzed the tectonic environment, crustal velocity structure in the source region, source parameters and rupture process, Coulomb failure stress changes, and 3-D features of the rupture plane of the Jiuzhaigou earthquake. Our results indicate the following: (1) The Jiuzhaigou earthquake occurred on an unmarked fault belonging to the transition zone of the east Kunlun fault system and is located northwest of the Huya fault. (2) Both the mainshock and aftershock rupture zones are located in a region where crustal seismic velocity changes dramatically. Southeast to the source region, shear wave velocity at the middle to lower crust is significantly low, but it rapidly increases northeastward and lies close to the background velocity across the rupture fault. (3) The aftershock zone is narrow and distributes along the northwest-southeast trend, and most aftershocks occur within a depth range of 5–20 km. (4) The focal mechanism of the Jiuzhaigou earthquake indicates a left-lateral strike-slip fault, with strike, dip, and rake angles of 152°, 74° and 8°, respectively. The hypocenter depth measures 20 km, whereas the centroid depth is about 6 km. The co-seismic rupture mainly concentrates at depths of 3–13 km, with a moment magnitude (Mw) of 6.5. (5) The co-seismic rupture also strengthens the Coulomb failure stress at the two ends of the rupture fault and the east segment of the Tazang fault. Aftershocks relocation results together with geological surveys indicate that the causative fault is a near vertical fault with notable spatial variations: dip angle varies within 66°–89° from northwest to southeast and the average dip angle measures ~84°. The results of this work are of fundamental importance for further studies on the source characteristics, tectonic environment, and seismic hazard evaluation of the Jiuzhaigou earthquake.  相似文献   

3.
The source parameters of the Bohai Sea earthquake, July 18, 1969 and Yongshan, Yunnan earthquake, May 11, 1974 were determined by full — wave theory synthetic seismograms of teleseismic P waves. P+pP+sP wereform were calculated with WKBJ approximation and real integral paths. One — dimensional unilateral, finite propagation source was also considered. By trail — and — error in comparing the theoretical seismograms with the observational ones of WWSSN stations, the source parameters were obtained as follow: for Bohai earthquake, φ=195°, δ=85°, λ=65°,M o=0.9×1019Nm,L=59.9km.V R=3.5km/s, ∧ R =160°; for Yongshan earthquake, φ=240°, δ=80°, ∧=150°,M o=1.3×1018Nm,L=48.8km,V R=3km/s, ∧ R =−10°, where φ is strike, δ dip angle, λ slip angle,M o seismic moment,L rupture length,V R rupture propagation speed. As III type fractures the faulting propagated along the fault planes, and ∧ R is the angle from the strike to the propagation direction. Yongshan earthquake showed complexity in its focal process, having four sub—ruptures during the first 60 seconds. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 1–8, 1991.  相似文献   

4.
Breakthrough point source model, extended earthquake source model is used to calculate more seismic source parameters in this paper. We express seismic source using higher degree moment tensors, to reduce a large number terms originally presenting in higher degree moment tensor representation, Haskell rupture model is used. We inverted the source parameters of Mani earthquake in Tibet using broad-band body wave of 32 stations of Global Seismograph Network (GSN), the results show that it is a strike-slip fault, rupture direction is 75° , rupture duration is 19 s, the fault plan is f =77° , d =88° , l =0° , the auxiliary plane is f =347° , d =90° , l =178° , and the fault dimension is 47 km′ 28 km. These results will give new quantitative data for earth dynamics and have practical meaning for seismic source tomography research.  相似文献   

5.
The boundary integral equation method(BIEM)is now widely used in numerical studies on earthquake rupture dynamics,and is proved to be a powerful tool to deal with problems on complex fault system.However,since this method heavily lies on the specific forms of Green's function and only the Green's function in full-space has a closed analytic expression,it is usually limited to a full-space medium.In this study,as a first step to extend this method to an arbitrary complex fault system in half-space,the boundary integral equations(BIEs)for dynamic strike-slip on vertical complex fault system in half-space are derived based on exact Green's function for isotropic and homogeneous half-space.Effect of the geometry of the complex fault system are dealt with carefully.Final BIEs is composed of two parts:contribution from full-space,which has been thoroughly investigated by Aochi and his co-workers by using the Green's function for full-space,and that from free surface,which is studied in detail in this study.  相似文献   

6.
利用2010~2016年阳江地区小震资料,对围绕广东阳江6.4级地震发震构造的NEE走向平冈断层的西南段及NW走向的程村断层展布的密集地震,经双差定位方法重新进行震源位置的修定,获得了1411个精定位震源资料。依据成丛地震发生在断层附近的原则,采用模拟退火算法及高斯-牛顿算法相结合的方式,较精确地获得了2个断层面的详细参数：即平冈断层西南段走向258°、倾角85°、倾向NW,与6.4级地震的震源机制解结果十分一致,断层长度约15km并穿过了其西南端海域抵达了对岸;程村断层走向331°、倾角88°、倾向NE,长度约28km,较已有结果更长、走向也朝NE向偏转了约15°。2条陡直断层近乎垂直相交于近海,在构造应力作用下均以走滑错动为主。  相似文献   

7.
The correlation of the scaled energy, ê = Es/M0, versus earthquake magnitude, Ms, is studied based on two models: (1) Model 1 based on the use of the time function of the average displacements, with a ω-2 source spectrum, across a fault plane; and (2) Model 2 based on the use of the time function of the average displacements, with a ω-3 source spectrum, across a fault plane. For the second model, there are two cases: (a) As τ ≒ T, where τ is the rise time and T the rupture time, lg(ê) ~ -Ms; and (b) As τ ≪ T, lg(ê) ~ -(1/2)Ms. The second model leads to a negative value of ê. This means that Model 2 cannot work for studying the present problem. The results obtained from Model 1 suggest that the source model is a factor, yet not a unique one, in controlling the correlation of ê versus Ms.  相似文献   

8.
The Kaoiki, Hawaii, earthquake with magnitude 6. 6 of November 16, 1983 was a strike-slip faulting event on a fault with large dip angle. The results for mechanisms of smaller events before and after the Kaoiki mainshock show that there were two kinds of mechanisms: (1) strike-slip on the fault with large dip angle; (2) slip on the crustal discontinuity plane with smaller dip angle, and systematic and alternative changes in the mechanisms were observed. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 139–149, 1991.  相似文献   

9.
Source extent parameters of the 1988 Lancang earthquake (M s=7.6) were estimated by computing the second-central moment of displacement pulses of far field long period SH waves. We inverted the source duration T, the fault length L and the directivity parameter D by the least squares, and obtained that T=11.77 s, D=15.05 km·s, and L=70.94 km. We also find that this event is a symmetrically bilateral rupture and fault segments in two opposite rupture directions have the same value of 35 km in length. Combining analysis of aftershock distribution, the results would imply that there is an area in the joint part of the rupture area of two main shocks, which is not broken yet during the main shocks. Due to the dislocation accompanied during the main shocks, the strain would be rearranged. The joint part has enough strength to accumulate enough strain energy to excite a larger aftershock.  相似文献   

10.
为深入理解汶川地震破裂的构造运动机制,本文选取典型的观测点,利用多种地质地貌标志测绘分析得到了汶川MS8.0地震发震断裂的近地表三维同震滑移矢量.结果显示,北川—映秀断裂上的白水河—高川破裂段北西盘沿88°方位角水平滑移2.58 m、垂直滑移3.70 m;安县—灌县断裂上的白鹿—汉旺破裂北西盘沿134°方位角水平滑移1.63 m,垂直滑移2.00 m;小鱼洞破裂带南西盘沿76°~79°方位角水平滑移2.15~2.71 m,垂直滑移1.36~1.51 m.平行的白水河—高川破裂段和白鹿—汉旺破裂段合计形成1.72 m右旋走滑和3.49 m垂直断裂带的NW向水平缩短,总滑移方向（106°）与断裂带整体走向（42°）呈64°夹角,整个龙门山推覆构造带处于斜向挤压的构造环境.结合震源过程反演成果的分析显示,斜滑的白水河—高川破裂段和逆冲型白鹿—汉旺破裂段可能是在汶川地震中最大的一次子事件过程以滑移分解的形式而同时破裂形成的,滑移分解作用使两条断裂以斜滑与逆冲组合的力学性质产生破裂而非相同性质的斜滑破裂.小鱼洞破裂以低角度斜滑为主,可能是安县—灌县断裂与北川—映秀断裂以滑移分解形式同时破裂的纽带.小鱼洞断裂是龙门山断裂带长期处于斜向挤压的构造环境的产物,不只是逆冲断裂系中的捩断层.  相似文献   

11.
The results of seismic deep reflection,high resolution refraction and shallow artificial seismic exploration indicate that the fault on the northern bank of the Weihe river is composed of two faults,one is the Yaodian-Zhangjiawan fault and the other is the Chuanzhang-Zuitou fault.The 22 km long Yaodian-Zhangjiawan fault of EW-striking starts from Chenjiagou via Yaodian town,Qianpai village,Bili village,Wujia town and Zhangjiawan to Jiajiatan.The 15 km long Chuanzhang-Zuitou fault striking near EW starts from Chuanzhang via Mabei to Zuitou.The Weihe fault offset the basement and upper crust,the reflecting layers of TQ,TN,TE and Tg are ruptured at depth of about 15 km.In the deep part,the Weihe fault and the secondary fault form a Y-shaped structure or a synthetic low angle intersection.The Weihe fault is a listric normal fault.The fault has obvious structural characteristics of a reversed-drag normal fault and a normal drag normal fault with the depth of 1 000 m,and also has the characteris-tics of syngenetic sediment.The Weihe fault is one of the faults which control the basin sediment,and it is the boundary fault of Xi’an depression and Xianyang salient.The depth of the fault decreases from the west to east gradually,the deep part intersects with the Lintong-Chang’an fault at the intersection part of Weihe River,Jinghe River and Bahe River and the shallow part connects with the Weinan-Jingyang fault.The seismic exploration re-sults indicate that no fault exists on southern bank of the Weihe River.  相似文献   

12.
Magnetotelluric response is studied for an inhomogeneous medium having conductivity varying linearly with depth as σ(z) =σ1+αz. For a medium having conductivity increasing linearly with depth, the phase of the impedance approaches 60° at long periods and the apparent resistivity becomes log (ρa) = 2 log (1.36/α1/3) — 1/3 log (T'). The asymptote of log (ρa, T'→∞) when plotted against log (T') has a constant gradient —1/3 and has an intercept on the log (T') axis, which equals 6 log (1.36/α1/3). When a homogeneous layer with a moderate thickness overlies an inhomogeneous half-space, this layer does not affect the asymptote, but it affects the cut-off period and pushes this toward the long period direction. For a medium having conductivity decreasing linearly with depth, the impedance is equivalent to that of a Cagniard two-layer model; the intercept period related to the thickness is T'0=σ1(h2/2)2. Homogeneous multilayer approximations to an inhomogeneous layer are also investigated, and it is shown that the fit to the model variation depends on the number of layers and the layer parameters chosen.  相似文献   

13.
Source model of Noto-Hanto-Oki earthquake tsunami of 7 February 1993   总被引：1，自引：0，他引：1  
A source model was discussed for a small tsunami accompanied by the Noto-Hanto-Oki earthquake (M s 6.6), striking Japan on 7 February, 1994. Assuming a fault model under the sea bottom, we estimated the focal parameters jointly, using synthesized tsunami source spectra as well as the tsunami numerical simulation. The fault proposed by this study consists of a plane sized 15×15 km, dipping N47°W with the dip angle of 42°, which is almost pure reverse fault (slip angle 87°) with a dislocation of 1 meter. The numerical simulation shows that the shallow sea in the source region caused a comparatively long recurring tsunami (the periods are 12–18 minutes) in spite of its small size. The model fault is corresponding to an aftershock area of this earthquake.  相似文献   

14.
We conducted moment tensor inversion and studied source rupture process for M S=7.9 earthquake occurred in the border area of China, Russia and Mongolia on September 27 2003, by using digital teleseismic P-wave seismograms recorded by long-period seismograph stations of the global seismic network. Considering the aftershock distribution and the tectonic settings around the epicentral area, we propose that the M S=7.9 earthquake occurred on a fault plane with the strike of 127°, the dip of 79° and the rake of 171°. The rupture process inversion result of M S=7.9 earthquake shows that the total rupture duration is about 37 s, the scalar moment tensor is M 0=0.97×1020 N·m. Rupture mainly occurred on the shallow area with 110 km long and 30 km wide, the location in which the rupture initiated is not where the main rupture took place, and the area with slip greater than 0.5 m basically lies within 35 km deep middle-crust under the earth surface. The maximum static slip is 3.6 m. There are two distinct areas with slip larger than 2.0 m. We noticed that when the rupture propagated towards northwest and closed to the area around the M S=7.3 hypocenter, the slip decreased rapidly, which may indicate that the rupture process was stopped by barriers. The consistence of spatial distribution of slip on the fault plane with the distribution of aftershocks also supports that the rupture is a heterogeneous process owing to the presence of barriers.  相似文献   

15.
The earthquake was modeled using regional broad-band stations in Greece (epicentral distances up to 340 km). Inversion of the amplitude spectra of complete waveforms (0.05–0.08 Hz), later confirmed by the forward waveform modeling, provided strike = 150°, dip = 70°, rake = 10°, scalar moment M o = 4.1e18 Nm, and depth of 8 km. As the aftershock distribution had the same strike, the earthquake was interpreted as a left-lateral strike slip. The fault length was estimated by combining observed mainshock spectra and synthetic spectra of a weak event, representing impulse response of the medium. This gave the fault length estimate of 16 to 24 km. Similar results were obtained by means of a true M w = 5 aftershock. The waveform modeling (0.05–0.20 Hz) was performed for the 20 × 10 km finite-extent fault, with a homogenous slip of 0.63 m. It showed that the rupture propagation along the 150° strike was predominantly unilateral, from NW to SE.  相似文献   

16.
On the basis of fault’s dynamic model of Knopoffet al. (1973), this paper has finally obtained a simple approximate formula to be able to estimate the recurrence time intervalT R of earthquake on strike-slip fault. Preliminary result holds thatμ andδ s — δ f have not much effect onT R . Leta is the ratio of the coseismic displacementD s to the total displacementD t in whole event course, i.e.,a =D s /D t , thena = 1/3 may represent the standard theoretical state in whichT R is independent onμ andδ s — δ f . At this time,T R is the arithmetic average ofs 0/v andkd/β, wheres 0 is the long-term preseismic accumulated slippage,v is fault’s average displacement rate,d is the fracture length on the fault of seismic focal region andβ is shear wave velocity. In addition,k =υ 0/aυ, whereυ 0 is the initial fracture velocity of actual structure at the coseismic instant. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, 187–194, 1992. This paper is a part of contracted item of State Seismological Bureau — Tectonic Physical Study of Earthquake Recurrence Period and Characteristic Magnitude.  相似文献   

17.
The great Sanhe-Pinggu M8 earthquake occurred in 1679 was the largest surface rupture event recorded in history in the northern part of North China plain. This study determines the fault geometry of this earthquake by inverting seismological data of present-day moderate-small earthquakes in the focal area. We relocated those earthquakes with the double-difference method. Based on the assumption that clustered small earthquakes often occur in the vicinity of fault plane of large earthquake, and referring to the morphology of the long axis of the isoseismal line obtained by the predecessors, we selected a strip-shaped zone from the relocated earthquake catalog in the period from 1980 to 2009 to invert fault plane parameters of this earthquake. The inversion results are as follows: the strike is 38.23°, the dip angle is 82.54°, the slip angle is -156.08°, the fault length is about 80 km, the lower-boundary depth is about 23 km and the buried depth of upper boundary is about 3 km. This shows that the seismogenic fault is a NNE-trending normal dip-slip fault, southeast wall downward and northwest wall uplift, with the right-lateral strike-slip component. Moreover, the surface rupture zone, intensity distribution of the earthquake and seismic-wave velocity profile in the focal area all verified our study result.  相似文献   

18.
Using the double-difference relocation algorithm, we relocated the 20 April 2013 Lushan, Sichuan, earthquake (M S 7.0), and its 4,567 aftershocks recorded during the period between 20 April and May 3, 2013. Our results showed that most aftershocks are relocated between 10 and 20 km depths, but some large aftershocks were relocated around 30 km depth and small events extended upward near the surface. Vertical cross sections illustrate a shovel-shaped fault plane with a variable dip angle from the southwest to northeast along the fault. Furthermore, the dip angle of the fault plane is smaller around the mainshock than that in the surrounding areas along the fault. These results suggest that it may be easy to generate the strong earthquake in the place having a small dip angle of the fault, which is somewhat similar to the genesis of the 2008 Wenchuan earthquake. The Lushan mainshock is underlain by the seismically anomalous layers with low-VP, low-VS, and high-Poisson’s ratio anomalies, possibly suggesting that the fluid-filled fractured rock matrices might significantly reduce the effective normal stress on the fault plane to bring the brittle failure. The seismic gap between Lushan and Wenchuan aftershocks is suspected to be vulnerable to future seismic risks at greater depths, if any.  相似文献   

19.
ｎｔｒｏｄｕｃｔｉｏｎＴｒａｎｓｉｅｎｔＳｗａｖｅｖｅｌｏｃｉｔｙｒｕｐｔｕｒｅ（ＴＳＶＲ）ｍｅａｎｓｔｈｅｖｅｌｏｃｉｔｙｖｏｆｆａｕｌｔｒｕｐｔｕｒｅｉｓｂｅｔｗｅｅｎＳｗａｖｅｖｅｌｏｃｉｔｙβａｎｄＰｗａｖｅｖｅｌｏｃｉｔｙα．Ｉｔｓｅ...  相似文献   

20.
To obtain the temperatureT and volumeV (or pressureP) dependence of the Anderson-Grüneisen parameter T , measurements with high sensitivity are required. We show two examples:P, V, T measurements of NaCl done with the piston cylinder and elasticity measurements of MgO using a resonance method. In both cases, the sensitivity of the measurements leads to results that provide information about T (,T), where V/V 0 andV 0 is the volume at zero pressure. We demonstrate that determination of T leads to understanding of the volume and temperature dependence ofq=( ln / lnV) T over a broadV, T range, where is the Grüneisen ratio.  相似文献   

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