Processes of the displacement field change of the 2009 April 6 M_W6.3 L’Aquila earthquake using persistent scatterer and small baseline methods

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.     

Co-seismic deformation derived from GPS observations during April 20th, 2013 Lushan Earthquake,Sichuan, China

We process the standard 30 s, static GPS data and the 1 s, high-rate GPS （HRGPS） data provided by the Crustal Movement Observation Network of China with GAMIT/GLOBK software package, and obtain the co- seismic displacements of near field and far field, and the epoch-by-epoch time series of HRGPS during Lushan earthquake. GPS data from about 20 sites in Sichuan province, which located between 40 and 450 km from the epicenter, are analyzed so as to study the characteristics of the static displacements and the dynamic crustal defor- mations, with periods ranging from several minutes to over a month. The result shows that： the static displacements caused by Lushan earthquake are limited to several centi- meters; the nearest station SCTQ at 43 km from the epi- center has the largest static displacement of about 2 cm, while the other stations generally have insignificant dis- placements of less than 5 mm. the stations in the east ofSichuan-Yunnan region shifts 5-10 mm toward the southwest, and the stations in the middle-west of Sichuan Basin moves indistinctively 1-2 mm toward the northwest; station SCTQ has the largest kinematic displacement of about 4 and 3 cm peak-to-peak on the north and east component, respectively, and is much greater than the static permanent displacement; for the stations located at a distance greater than 150 km from the epicenter, the kinematic motions are generally insignificant; exception- ally, station SCNC and station SCSN in central Sichuan Basin have significant kinematic motions although they are more than 200 km away from the epicenter.     

福建仙游地震序列的震源机制解

1,209 earthquakes occurred in Xianyou, Fujian from August 4, 2010 to October 4, 2013. The largest earthquake was ML5.0 on September 4, 2013. In order to study the Xianyou earthquake sequence and understand the causative structure and stress field of Xianyou, the focal mechanism solutions of six earthquakes （ ML 〉 3. 5 ） in the Xianyou earthquake sequence are calculated using the broadband digital data of the Fujian Seismic Network with the seismic moment tensor inverse method. The results show that the focal faults of the six earthquakes are similar, which are all strike-slip faults striking to the northwest with high dip angles. The direction of the principal compressive stress axes is near SN, which is different from the stress field of Fujian region. The Xianyou earthquake sequence may have been induced by the stress adjustment after the impoundment of Jinzhong reservoir.     

群测群防网络在防震减灾工作中的作用

0 前言 群测群防,简单地说就是依靠群众的力量,共同防御地震灾害。群测群防队伍在过去几十年的地震短临预报中发挥着专业队伍难以替代的作用。     

2014年2月12日于田MS7.3地震前形变异常

The Yutian earthquake with Ms7. 3 happened on February 12, 2014. The precursor monitoring ability is weak in that area. We found tendency anomalies and middle- and short-term anomalies from metal pendulum tilt measurements in Hotan seismic station before the earthquake. And we also compared the anomalies with that of the Ms7. 3 Yutian earthquake on March 21, 2008. The tendency anomalies measured by the metal pendulum tiltmeter appeared since 2012 as tilting eastward. While the middle- and short-term anomalies were characterized by acceleration, pause and rapid change of tilt rate in two directions. The tendency anomalies of metal pendulum tilt records are the same before the two earthquakes. They both happened in the east direction. However, there are differences in duration, characteristic and earthquake intervals for the middle- and short-term anomalies.     

关于完善西藏防震减灾工作中地方法规建设的思考

随着以法治国方略的实施和中国特色社会主义法律体系的初步建立,以《中华人民共和国防震减灾法》为基本框架的防震减灾法规体系得到不断完善。长期以来西藏受各种因素的影响,自治区防震减灾地方立法进展缓慢,对此,结合西藏防震减灾法制建设实际,在完善西藏防震减灾地方立法方面提出自己的一些观点和措施。     

据地壳速度结构推测1668年山东郯城8?级大地震震中

The deep structure features around Tancheng M8 /2 earthquake occurred in 1668 have been analyzed. Based on the crustal velocity structure obtained from travel-time tomographic inversion, especially the low velocity zones in middle crust and Moho depths, the deep velocity structure distribution in the area of 34° ~ 36°N, 118° ~ 119°E is scanned along the latitude, longitude and oblique directions, and the corresponding crustal velocity profiles are obtained. By comparison, we take the area with velocity features coincident to the deep structure of the 1668 Tancheng M8/2 earthquake as the deduced epicenter, which is at 34. 8° ~35. 2°N, 118. 2° ~ 118. 7°E, and the reasonable location is 35. isN, 118. 6°E, and the focal depth is 20km.     

汶川8.0级地震前龙门山断裂带孕震构造运动特征分析?

On the basis of elastic rebound theory, using the horizontal velocity field of the Chinese mainland calculated from GPS data during three observation periods from 1999 to 2007, the velocity components that are parallel and plumb to the fault zone are calculated respectively for different periods, and then relative ground movements of two sides of the fault zone are analyzed with power function fitting and graphics. The results show that the relative ground movement shows right-lateral shear deformation before the Wenchuan Ms8. 0 earthquake, and at the same time the movement was hindered by the Longmenshan fault zone. Thus, this result has positive significance for distinguishing the elastic strain energy accumulation and deformation anomaly in an earthquake preparation process, and for conducting further research on earthquake prediction.     

2013 年芦山MS7.0 地震前甘孜台地电阻率变化分析

A trend increase in apparent resistivity has been observed in the N30°E monitoring direction at Garze Seismic Station since July 2011. This increase trend in geo-electric resistivity has been observed in the N60°W direction since 2012. During the period of the increase, the national highway No.317 was expanded in the monitoring area, so the potential electrodes in the N30°E direction had to be moved 10m towards the current electrodes. We interpreted the electric sounding data of Garz6 Seismic Station with a horizontally layered model. Analysis based on this model showed that the shift of potential electrodes can cause a 4 l-l.m rise to the measurements in the N30°E direction. Therefore, apparent resistivity of the two directions increased in the same time in 2012 after offsetting the effects from electrodes shift. Sensitivity coefficients of the two observation directions were also obtained using the model. Sensitivity coefficients of both directions were negative for the shallow layers, which can well explain the unexpected annual variations of Garze Seismic Station. In order to quantitatively analyze the effects from the expansion of the national highway on the observation, we constructed a finite element model based on the electrical structure. Analysis results also suggested that the expansion of the national highway could only cause a 0. 15 Ω·m decrease in the N60°W monitoring direction and 0. 1 Ω· m increase in the N30°E direction. Additionally, the valley values of annual variation of 2013 were distinctively higher than that of other years since 2008, meaning that there was an abnormal rise in apparent resistivity in the two observation directions at Garz~ Seismic Station before the Lushan earthquake. However, the rise was contrary to the decline variation before the Wenchuan earthquake. Therefore, it is still unsure whether or not the rise variation is related to the Lushan earthquake.     

2014年于田MS7.3地震产生的静态库仑应力变化及对周边断层的影响

This paper calculates the static Coulomb stress changes generated by four earthquakes in the Yutian area during 2008 ~ 2014 separately, then discusses the triggering influence, their accumulated Coulomb stress changes and their influence on nearby faults. The results indicate that the Ms5. 5 earthquake in 2011 and the Ms7. 3 earthquake in 2014 are both in the regions where the Coulomb stress change is positive, the stress changes are 0. 004MPa and 0. 021MPa, respectively, meaning they are triggered by prior earthquakes. The Ms6. 2 earthquake in 2012 occurred in the place where Coulomb stress change was negative, so it is postponed by the prior earthquakes. The image of Coulomb stress changes of the Ms 7. 3 earthquake in 2014 is in accord with aftershocks （ML ≥ 3. 0 ） distribution, but some regions on the fault where the Coulomb stress change is positive have few aftershocks, and strong aftershocks may occur at these districts in future. In addition, this paper calculates the Coulomb stress change on nearby faults, and finds that the Coulomb stress changes of different elements in the GGC fault are very different, and must receive strong triggered-influence, though the result may be influenced by the input finite fault model, so there is still a large earthquake-risk. The GGN, PLC, PLW and LBW faults were also triggered by the four earthquakes occurring between 2008 ~ 2014. Their maximum Coulomb stress changes all exceed 0. 002MPa, so they also have a strong earthquake hazard.     

Strong ground motion simulation for the 2013 Lushan M_W6.6 earthquake,Sichuan, China,based on the inverted and synthetic slip models

It is well known that quantitative estimation of slip distributions on fault plane is one of the most important issues for earthquake source inversion related to the fault rupture process. The characteristics of slip distribution on the main fault play a fundamental role to control strong ground motion pattern. A large amount of works have also suggested that variable slip models inverted from longer period ground motion recordings are relevant for the prediction of higher frequency ground motions. Zhang et al. （Chin J Geophys 56：1412-1417, 2013） and Wang et al. （Chin J Geophys 56：1408-1411,2013） published their source inversions for the fault rupturing process soon after the April 20, 2013 Lushan earthquake in Sichuan, China. In this study, first, we synthesize two forward source slip models： the value of maximum slip, fault dimension, size, and dimension of major asperities, and comer wave number obtained from Wang＇s model is adopted to constrain the gen- eration of k-2 model and crack model. Next, both inverted and synthetic slip models are employed to simulate the ground motions for the Lushan earthquake based on the stochastic finite-fault method. In addition, for a comparison purpose, a stochastic slip model and another k-2 model （k 2 model II） with 2 times value of comer wave number of the original k-2 model （k 2 model I） are also employed for simulation for Lushan event. The simulated results characterized by Modified Mer- calli Intensity （MMI） show that the source slip models based on the inverted and synthetic slip distributions could capture many basic features associated with the ground motion patterns. Moreover, the simulated MMI distributions reflect the rupture directivity effect and the influence of the shallow velocity structure well. On the other hand, the simulated MMI bystochastic slip model and k 2 model II is apparently higher than observed intensity. By contrast, our simulation results show that the higher frequency ground motion is sensitive to the degree of sli     

简易远震警报器的制作与使用

本文介绍了一款位移触发远震警报器的制作方法与使用情况,由此提高了速报地震的报警率,有效减少了台站在地震速报中的晚报、漏报现象。     

汶川8．0级特大地震汉源县震害特点与烈度异常成因探讨

本文在汉源县地震灾害调查的基础上,通过收集前人在该区已取得的成果资料,采用综合分析、类比等方法,对汉源县地震烈度异常区震害及造成异常的原因进行了分析探讨。汉源县建筑物破坏形式以水平地震作用造成的“X”型剪切破坏为主,竖向地震造成的破坏较少。地震波传播路径、场地土层条件和地形地貌条件三者的耦合是造成汉源县烈度异常的主要原因,其中场地土层中占优势厚度的砾石层是造成场地地震波放大的主要内因。本文取得的初步结论为更加深入地科学研究本区地震烈度异常的原因提供了新思路。     

Preliminary results of strong ground motion simulation for the Lushan earthquake of 20 April 2013, China

The earthquake occurred in Lushan County on 20 April, 2013 caused heavy casualty and economic loss. In order to understand how the seismic energy propagates during this earthquake and how it causes the seismic haz- ard, we simulated the strong ground motions from a rep- resentative kinematic source model by Zhang et al. （Chin J Geophys 56（4）：1408-1411, 2013） for this earthquake. To include the topographic effects, we used the curved grids finite difference method by Zhang and Chen （Geophys J Int 167（1）：337-353, 2006）, Zhang et al. （Geophys J Int 190（1）：358-378, 2012） to implement the simulations. Our results indicated that the majority of seismic energy con- centrated in the epicentral area and the vicinal Sichuan Basin, causing the XI and VII degree intensity. Due to the strong topographic effects of the mountain, the seismic intensity in the border area across the northeastern of Boxing County to the Lushan County also reached IX degree. Moreover, the strong influence of topography caused the amplifications of ground shaking at the moun- tain ridge, which is easy to cause landslides. These results are quite similar to those observed in the Wenchuan earthquake of 2008 occurred also in a strong topographic mountain area.     

Co- and post-seismic surface deformation and gravity changes of Ms7.0 Lushan,earthquake

On April 20, 2013, an earthquake with mag- nitude 7.0 occurred in the southwest of the Longmenshan fault system in and around Lushan County, Sichuan Province, China. This devastating earthquake killed hun- dreds of people, injured 10 thousand others, and collapsed countless buildings. In order to analyze the potential risk of this big earthquake, we calculate the co- and post-seismic surface deformation and gravity changes of this event. In this work, a multilayered crustal model is designed, and the elastic dislocation theory is utilized to calculate the co- and post-seismic deformations and gravity changes. During the process, a rupture model obtained by seismic waveform inversion （Liu et al. Sci China Earth Sci 56（7）： 1187-1192, 2013） is applied. The time-dependent relaxation results show that the influences on Lushan and its surrounding areas caused by the Ms7.0 Lushan earthquake will last as long as 10 years. The maximum horizontal displacement, vertical uplift, and settlement are about 5 cm, 21.24 cm, and 0.16 m, respectively; the maximal positive and nega- tive values of gravity changes are 45 and -0.47 μGal, respectively. These results may be applied to evaluate the long-term potential risk caused by this earthquake and to provide necessary information for post-earthquake reconstruction.     

fmax and fault zone property of Lushan earthquake of 20 April 2013, Sichuan,China

In this study, we determined fnax from near- field accelerograms of the Lushan earthquake of April 20, 2013 through spectra analysis. The result shows that the values of fmax derived from five different seismography stations are very close though these stations roughly span about 100 km along the strike. This implies that the cause offmax is mainly the seismic source process rather than the site effect. Moreover, according to the source-cause model of Papageorgiou and Aki （Bull Seism Soc Am 73：693-722, 1983）, we infer that the cohesive zone width of the rupture of the Lushan earthquake is about 204 with an uncertainty of 13 m. We also find that there is a significant bulge between 30 and 45 Hz in the amplitude spectra of accel- erograms of stations 51YAL and 51QLY, and we confirm that it is due to seismic waves＇ reverberation of the sedi- mentary soil layer beneath these stations.     

玉树MS 7. 1 地震同震效应模拟与绝对重力检验

Using the results of aftershock relocation, inversion on seismic waves and InSAR results, and surface rupture displacements obtained by geological survey after the earthquake, this paper constructs a fault model of the Yushu Ms7. 1 earthquake. Based on rectangular dislocation theory in an elastic-viscoelastic layered medium, we have simulated the co- seismic deformation and gravity change with gravitational effect considered. The pictures show that the absolute gravity measuring point is beside the extremum of coseismic gravity change, and the numerical value reaches 25.02 x 10-Sm. s-2. After a discussion about the gravity changes before the earthquake and the coherence consistency between two FG-5 absolute gravimeters, we think that the measured value 27.2 × 10^-8 m· s^-2 at Yushu station is coseismic gravity change. It＇s coincident with the simulation results based on dislocation theory. Therefore it is a good tool to test the near-field changes found by dislocation theory.     

A study on the uncertainties of the centroid depth of the 2013 Lushan earthquake from teleseimic body wave data

Centroid depth of earthquakes is essential for seismic hazard mitigation. But, various studies provided different solutions for the centroid depth of the damaging 2013 Lushan earthquake, thus hindering further studies of the earthquake processes. To resolve its centroid depth and assess the uncertainties, we apply the teleseismic cut and paste method to invert for centroid depth with teleseismic body waves in the epicentral distance of 300-90~. We performed the inversion for P waves only as well the case of both P and SH waves and found that both cases lead to depth solutions with difference less than 0.5 km. We also investigated the effects on depth inversion from azimuth gap of seismic stations, source duration, and comer fre- quency of filter. These various tests show that even azi- muthal distribution of seismic stations is helpful for accurate depth inversion. It is also found that estimate of centroid depth is sensitive to source duration. Moreover, the depth is biased to larger values when corner frequency of low-pass filter is very low. The uncertainty in the velocity model can also generate some error in the depth estimation （- 1.0 km）.With all the above factors consid- ered, the centroid depth of Lushan earthquake is proposed to be around 12 km, with uncertainty about 2 km.     

应对汶川特大地震波及乐山事件的做法及思考

2008年5月12日汶川8.0级地震是有史以来对乐山市波及范围最广、人员伤亡最多、经济损失最大、社会影响最强烈的地震。本文回顾了近几年乐山市在地震应急准备方面所做的工作和汶川特大地震波及乐山后的应急工作,认为坚持不懈地抓好地震应急准备是做好大地震之后应急工作的重要前提,及时有效地开展应急工作是防震减灾部门的重要职责,震后恢复重建中防震减灾部门可以发挥重要作用。     

叠溪地震和地震地质概说

1调查经过1933年8月25日大约在下午2时半,四川茂县之北叠溪,忽然发生大地震,即时间附近群山崩倒,叠溪城全部毁灭,岷江断流。叠溪周围30里内,属于强烈地震区,在这一范围内,任何房屋庐舍,全部破坏,群山崖壁,全部崩坍。在叠溪圆径百里之内,所有道路都被破坏,不能通行。邮电线路,全部不通。当时只知茂汶