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1.
We successfully employ an automatic centroid moment tensor(CMT) inversion system to infer the CMT solutions of the February 12,2014 MS7.3 Yutian,Xinjiang earthquake using near-field seismic waveforms(4° < △ < 12°) observed by the virtual China seismic networks,which have been recently set up.The results indicate that this event occurred on a rupture plane(strike 243°,dip 70°,and rake-18°),showing left-lateral strike-slip faulting with a minor normal-faulting component.The centroid in the horizontal direction is located nearly 13 km east of the epicenter(36.123° N,82.499° E),and the best-fitting centroid depth is around 10 km.The total scalar moment,M0,is retrieved with an average value of 3.05 × 1019N·m,corresponding to moment magnitude MW6.92.Most of the energy is released within about 14 s.Moreover,we discuss about the potential application of this system in earthquake disaster decision. 相似文献
2.
The time series of coordinates of a large number of GPS stations in the world,processed by Prof. Geoffrey Blewitt with GIPSY software are available at http://geodesy. unr. edu.Based on the time series of coordinates in the global reference frame of IGS08 at more than250 stations of continuous GPS observations,downloaded from the website,the co-seismic displacements of the M7. 3 Kyushu earthquake on April 16,2016 in Japan and the preseismic strain accumulations and displacements in the regional reference frame were obtained. The station of continuous GPS observation at BJFS near Beijing has been quite stable in displacement in the eastern part of China for more than 17 years since the beginning of its operation,and this station is used as the core station in the regional reference frame for the pre-seismic displacement of the Kyushu earthquake of M7. 3. The main feature of the pre-seismic displacements of the Kyushu earthquake is characterized by locking in the crust at and near the epicenter. The anomalous pre-seismic strain accumulation developed in an area of anomalous accumulation of the shear strain component of γ1 on the northeast side of the epicenter,with increasing size of the area and increasing magnitude in γ1. The largest area covered by the anomalous γ1 is about 2000 km2. The change in the E component at BJFS since November 26,2015 was caused by the replacement of the receiver and the antenna at the station. In order to study the shortterm change in displacements at stations at and near the epicenter,the time series at 3 stations with continuous GPS observations,2 at SUWN and DAEJ in south Korea and 1 at BJSH near Beijing were analyzed. The analysis shows that the displacements at the 3 stations have been quite stable in the same manner in east Asia. Thus,BJSH is used as the core station in the regional reference frame of displacement and the displacement time series show that there were no significant short term anomalies before the earthquake. 相似文献
3.
On the basis of textual research on the historical earthquake data and the field investigation of 1219 A.D.Guyuan earthquake,we suggest that there is only one strong earthquake occurred in Guyuan area in 1219 A.D.,instead of two or three strong earthquakes.We further suggest that the earthquake parameters recorded in the present earth-quake catalogs are not definite and should be modified.The occurrence time of this earthquake should be about 11 am,August 7,1219 A.D.and the heavily-damaged area of this earthquake,the VIII intensity area,should be lo-cated among the regions of Guyuan,Pingliang and Longde county cities.The epicenter area should be near Gu-yuan city.The magnitude of this earthquake is about 7 and it has intensity about larger than or equal to IX within the epicenter area.The major axis direction of the heavily-damaged area strikes in north-northwest that is ap-proximately consistent with the strike of the Liupan Shan thrust fault zone.The new tectonic activity of the Liupan Shan thrust fault zone resulted in the M7 Guyuan earthquake in 1219 A.D. 相似文献
4.
Rupture process of the 2015 Pishan earthquake from joint inversion of InSAR,teleseismic data and GPS
An earthquake of Mw6.4 occurred in Pishan County in Xinjiang Province, northwestern Tibetan Plateau, on July 3,2015. The epicenter was located on an active blind thrust system located at the northern margin of the Western Kunlun Mountain Orogenic Belt southwest of the Tarim Basin. We constructed a shovel-shaped fault model based on the layered-crust model with reference to the seismic reflection profile, and obtained the rupture process of the earthquake from the joint inversion of Interferometric Synthetic Aperture Radar(InSAR) measurements, far-field waveform data, and Global Positioning System(GPS) data. The results show that the seismic fault dips southward with a strike of 109°, and the rupture direction was essentially northward. The fault plane rupture distribution is concentrated, with a maximum recorded slip of 73 cm. The main features of the fault are as follows: low inclination angle(25°–10°), thrust slip at a depth of 9–13 km, rupture propagation time of about 12 s, no significant slip in soft or hard sedimentary layers at 0–4 km depth and propagation from the initial rupture point to the surrounding area with no obvious directionality. The InSAR time-series analysis method is used to determine the deformation rate in the source region within 2 years after the earthquake, and the maximum value is ~17 mm yr-1 in the radar line-of-sight direction. Obvious post-earthquake deformation is evident in the hanging wall, with a similar trend to the coseismic displacement field. These results suggest that the Pishan earthquake has not completely released the accumulated energy of the region, given that the multilayer fold structure above the blind fault is still in a process of slow uplift since the earthquake. Post-earthquake adjustment models and aftershock risk analysis require further study using more independent data. 相似文献
5.
In this paper, we firstly analyze the ＂3,400 travel time table＂ used for a long time in Xinjiang Seismological Network to obtain the velocity structure models in accord with the table by fitting. Then we fit the velocity of all seismic phases recorded in Xinjiang region in January 2009 ~ December 2013. Simulation analysis is done on the reliability and stability of the velocities, and a concept is proposed for building subarea crustal velocity models according to partitioning of seismic cluster regions. The crustal velocity model suitable for the Yutian area is fitted with the data of all phases of seismic events within a radius of 1 ° around the 2014 Yutian Ms7. 3 earthquake since January 2009, and the model is applied to the relocation of the Yutian Ms7. 3 earthquake and determination of focal depths of the earthquake sequence. 相似文献
6.
The 2008 Wenchuan earthquake has a significant impact on the seismicity of nearby regions. The Longnan earthquake which occurred on September 12,2008 in Gansu Province was out of the aftershock zone. Reliable source parameters are essential for understanding the seismogenic process of this earthquake. Therefore,three approaches are adopted to study the source parameters of this event. The focal mechanism is obtained with the g CAP method that takes non-Double-Couple(non-DC)component into account. The two fault planes are NP1:150°/45°/81° and NP2:342°/45°/98°,while the non-DC component is about 53%. The focal depth is 1. 6 km,which indicates the Longnan earthquake is a shallow event. Furthermore,this result is also in good agreement with results obtained with two other approaches:amplitude spectra of Rayleigh wave and surface displacement from In SAR measurement. To analyze the cause of the event,coulomb failure stress change caused by the Wenchuan earthquake on the Longnan earthquake fault plane is calculated. The result shows that coulomb stress change is 30 k Pa around the Longnan earthquake hypocenter,which exceeds the typical triggering threshold of 10 k Pa. The research indicates that the Wenchuan earthquake probably promote the happening of the Longnan earthquake. 相似文献
7.
Using a time series method that combines both the persistent scatterer and small baseline approaches, we analyzed 9 scenes Envisat ASAR data over the L＇Aquila earthquake, and obtained a Shocke＇s displacement field and its evolution processes. The results show that： （1） Envisat ASAR clearly detected the whole processes of displacement field of the L＇Aquila earthquake, and distinct variations at different stages of the displacement field. （2） Preseismic creep displacement → displacement mutation when faulting → constantly slowed down after the earthquake. （3） The area of the strongest deformation and ground rupture was a low-lying oval depression region to the southeast. Surface faulting within a zone of about 22 km× 14 km, with an orientation of 135°, occurred along the NW-striking and SW-dipping Paganica-S. Demetrio normal fault. （4） In analyzing an area of about 54 km x 59 km, bounded by north-south axis to the epicenter, the displacement field has significant characteristics of a watershed： westward of the epicenter shows uplift with maximum of 130 mm in line-of-sight （LOS）, and east of the epicenter was a region with 220 mm of maximum subsidence in the LOS, concentrating on the rupture zone, the majority of which formed in the course of faulting and subsequence. 相似文献
8.
For earthquake and tsunami early warning and emergency response,the earthquake epicenter and magnitude should be determined rapidly and correctly.Using high-rate GPS observations,we can readily obtain precise and high resolution displacement time series and the seismic waveforms during the earthquake.In this paper,a new algorithm is proposed for estimating the earthquake epicenter and magnitude with the seismic waveforms derived from high-rate GPS data during the earthquake.A case study of the 2008 Wenchuan earthquake is conducted from 1 Hz GPS data and the epicenter and magnitude are determined.Compared with the results issued by the China Seismological Bureau,the estimation error of the epicenter and the magnitude is about 12 km and 0.1 magnitude unit,respectively.It has shown that high-rate GPS could be a new tool feasible for estimating the earthquake epicenter and magnitude,independent of or combined with seismometers. 相似文献
9.
Using the focal mechanism solutions and slip distribution model data of the Taiwan Straits MS7.3 earthquake on September 16, 1994, we calculate the static Coulomb stress changes stemming from the earthquake. Based on the distribution of aftershocks and stress field, as well as the location of historical earthquakes, we analyze the Coulomb stress change triggered by the Taiwan Straits MS7.3 earthquake. The result shows that the static Coulomb stress change obtained by forward modeling based on the slip distribution model is quite consistent with the location of aftershocks in the areas far away from the epicenter. Ninety percent of aftershocks occurred in the stress increased areas. The Coulomb stress change is not entirely consistent with the distribution of aftershocks near the epicenter. It is found that Coulomb stress change can better reflect the aftershock distribution far away from the epicenter, while such corresponding relationship becomes quite complex near the epicenter. Through the calculation of the Coulomb stress change, we find that the stress increases in the southwest part of the Min-Yue (Fujian-Guangdong) coastal fault zone, which enhances the seismic activity. Therefore, it is deemed that the sea area between Nanpeng Island and Dongshan Island, where the Min-Yue coastal fault zone intersects with the NW-trending Shanghang-Dongshan fault, has a high seismic risk. 相似文献
10.
The Qilian Mountain active source network data was processed using the methods of stacking, cross-correlation and interpolation, and the airgun travel time variation characteristics of P and S waves around the January 21, 2016 MS6.4 Menyua, Qinghai earthquake. The results show that about 6 months before the earthquake, the relative travel time of three stations near the epicenter showed a declined change (travel time decrease), and such a change of low value anomaly was recovered about 3 months before the earthquake. The travel time decrease then appeared again, and the earthquake occurred during the recovery process. The maximum decrease of the S-wave travel time was 18ms, and the change in travel time returned to normal after the earthquake. The variation trend of the 3 stations is consistent, including the S-wave travel time change of station ZDY38, which is nearest to the epicenter and changed obviously, and the variation range of the travel time is smaller at the stations afar. This variation pattern is related to the position of the seismic source. The shorter travel time means the velocity increase, which may be related to the regional stress accumulation. 相似文献
11.
12.
近年来,地磁谐波振幅比方法在国内得到较广泛的应用,并成为一种较为有效的地震预测方法。本文利用谐波振幅比方法,对2017年11月23日重庆武隆5.0级地震震中附近台站的地磁三分量数据进行计算,并分析了各台站10~60min周期谐波振幅比值异常特征。研究发现,异常台站几乎均位于震源机制解的拉张区(P波向下的区域),具有象限分布特征;异常台站NS向谐波振幅比值变化存在分层现象,短周期(浅部)的变化与长周期(深部)变化成相反相位,从电磁学机理看,浅部与深部之间存在EW向的面电流;近震中台站的异常低点时间存在由长周期(深部)向短周期(浅部)迁移的现象。 相似文献
13.
利用乌什台数字化前兆形变观测资料，分析乌什MS 4.5级地震前乌什台水管倾斜仪、洞体应变仪数据变化情况。通过对比分析发现:地震前，洞体应变仪北南分量数据曲线正常，东西分量数据曲线加速拉张，05:14-20:32拉张幅度达到7.40×10-7，7月19日5时至20日16时乌什洞体应变仪东西分量快速拉张了9.20×10-7；7月19日5-19时，水管倾斜仪北南分量数据曲线正常，东西分量数据曲线反向西倾7.13ms，且05:59-06:06、07:36-07:46、18:42-18:56数据掉格，水管倾斜仪异常结束后1小时，在洞体应变仪异常过程中发生了乌什MS 4.5级地震。水管仪东西分量震前反向西倾，洞体应变仪东西分量震前拉张加速，短临异常明显，且2套形变观测震前异常时间同步性较好。 相似文献
14.
强震临震微波动是强震临震阶段优势频率集中在11～16 Hz、频谱形态较为整齐的临震异常脉动记录。利用"兰州临震微波动实时监控与跟踪系统"的数据资料,对2021年5月22日玛多7.4级地震震中200 km半径的范围内台站的临震微波动事件进行分析。认为震前距离震中67 km的巴颜喀拉台EW通道存在显著异常,达到杨立明提出的异常跟踪指标;10个测震台站中的8个在本次地震前记录到了临震微波动事件,震中南侧台站记录到的事件多于北侧。 相似文献
15.
分析距离九寨沟MS7.0地震震中分别为65 km、254 km和238 km的松潘地磁台、成都地磁台和天水地磁台2017年连续观测结果,发现九寨沟地震前,松潘地磁台出现异常变化,主要表现为2017年5月开始,松潘地磁台长时间垂直分量累积变化量达40 nT。短时间内也存在地磁场突变,最高可达10 nT,而成都地磁台和天水地磁台地磁场无明显异常。通过对观测数据的详细检查发现松潘地磁台很多观测日的最后一个观测值与后一观测日的第一个观测值相差超过1 nT,因此认为九寨沟地震前观测数据的异常是由观测系统异常导致。对三个台站地磁场垂直分量日变化的统计分析发现垂直分量在不同时段相关性保持一致,说明地震前短时间内不存在地磁垂直分量的明显异常变化,三个台站地磁场日变化的差异是由地下介质性质不同导致。岩石圈磁场在震中西侧区域出现正负异常交替现象,这可能与九寨沟地震的孕育有关。 相似文献
16.
基于2021年5月21日漾濞M_S6.4地震震中附近50 km范围内15个地震观测台站记录的2020年11月1日—2021年5月30日的气枪震源信号,采用互相关时延检测技术提取这15个台站各自稳定震相(Sg震相)的走时变化时间序列,并对漾濞M_S6.4地震前后各台站的走时变化特征进行分析。结果表明:(1)漾濞M_S6.4地震前10天左右,有4个台站走时开始出现异常,其中,Ey211和Ey213台走时呈"V"型变化结构,Ey210和CHT台走时呈上升趋势。(2)漾濞M_S6.4地震后短期内,大部分台站走时出现了明显的趋势性变化,以维西—乔后—巍山断裂为界,断裂带两侧台站走时变化趋势存在明显差异,断裂以东的EYA、HDQ、YSW09台走时呈上升趋势,变化最为显著的为HDQ台,走时差变化量为0.067 s;而断裂带以西的所有台站在漾濞M_S6.4地震当天(或震后1～2天)开始出现明显趋势性下降,走时下降持续时间在4～9天间,走时差变化量在-0.053～-0.201 s间,其中走时差下降量最大为53 285台,最小为CHT台。 相似文献
17.
从岩石应力-应变的本构关系出发,以能够反映岩石应变变化的地应变观测数据作为"响应量",通过库伦应力触发模型的加卸载响应比计算方法,计算2017年8月8日九寨沟M_S7.0地震前震中及周边500km范围内应变观测的加卸载响应比结果。结果显示,基于应变观测的加卸载响应比方法能够较好地从潮汐频段提取地震前LURR异常,九寨沟地震前,300km范围内的多个应变观测台站出现LURR异常,其中相距96km的两水台EW分量Y值最大达到3.27;LURR空间演化特征显示,在震前约9个月内震中及周边地区陆续出现异常"集中—增强—减弱"过程,证明该地区在长期应力累积的背景下,应力的不断累积增强导致震中及附近区域的岩石出现不断损伤或弱化,最终位于树正断裂上的应变能积累超过了介质强度而引发了此次地震。 相似文献
18.
2020年7月12日，河北唐山发生MS5.1地震，河北省地震预警系统成功地处理并产出了这次地震预警各种结果数据，本文借助此次地震对河北地震预警网内震中距200km范围内台站产出质量以及地震预警前5次处理结果进行详细分析。此次地震发生在河北地震预警网内，平均台间距为10km，首台触发后3s、震后6s发布首次处理结果，与编目结果相比，震级偏差为-1.3，震中位置偏差为2.6km，盲区半径为18km。随着参与定位台站数量增多，震级与位置偏差越来越小，但震级仍整体偏小。河北地震预警网台站产出质量整体较高，其中烈度台作为地震预警最重要的组成部分，是决定预警效果的关键因素。本次地震震中距200km范围内，烈度台平均信噪比为48，震中距50km范围内平均信噪比为112，符合预警系统对信噪比的要求。本次地震预警结果表明，河北地震预警网内台站布局基本合理，波形质量较高，地震预警系统处理软件在本次地震中预警产出效果较好，已经具备了一定的地震预警能力。 相似文献
19.
分析2016年10月20日射阳MS4.4地震前地下流体典型异常特征并对其机理进行讨论。该地震前的地下流体前兆异常（1）从时间进程看可分为中期趋势背景异常和短期异常；（2）从空间演化上看，在中期趋势背景阶段，异常分布在离震中300 km范围内，其在起始时间上表现为从震中向外围迁移继而向震中靠拢的特点。相较于中期趋势背景阶段异常；短期异常在空间上向震中收缩，分布在离震中100~200 km范围内，其在起始时间上，表现为向震中靠拢的特点。井水温异常变化可能是区域应力加载作用的产物，而离子浓度的变化可能是水岩反应加剧引起的。 相似文献
20.
地震地下流体在地震预测研究与震情跟踪方面发挥着重要作用,本文对2021年5月22日青海玛多MS7.4地震前震中附近地下流体观测资料及异常特征进行系统分析,并结合震前预测过程进行了回顾性总结。结果表明,玛多MS7.4地震震中距500km范围内存在5项异常,其中4项为短期异常,主要出现在震前2～3个月。异常在空间上分布不均匀,主要位于玛多MS7.4地震震中的东北部和西南部,整体呈现出由外围向震中收缩的迁移特征,且玛多MS7.4地震和2010年青海玉树MS7.1地震在异常特征和应力加载作用方面具有较好的相似性。研究结果为地震监测能力较低地区积累了震例资料,对于提升强震地下流体前兆异常认识及未来震情趋势判定水平具有一定的参考意义。 相似文献