Velocity structure of the crust and upper mantle in Xingtai earthquake region and its adjacent area

ＶｅｌｏｃｉｔｙｓｔｒｕｃｔｕｒｅｏｆｔｈｅｃｒｕｓｔａｎｄｕｐｐｅｒｍａｎｔｌｅｉｎＸｉｎｇｔａｉｅａｒｔｈｑｕａｋｅｒｅｇｉｏｎ　ａｎｄ　ｉｔｓａｄｊａｃｅｎｔａｒｅａＺｈｉ－ＰｉｎｇＺＨＵ；（祝治平）Ｘｉａｎ－ＫａｎｇＺＨＡＮＧ；（张称康）Ｙｕ...     

3-D velocity images of the crust and upper mantle of the Tianshan area

（胥颐，朱介寿，刘志坚，张华卿，朱燕）３－ＤｖｅｌｏｃｉｔｙｉｍａｇｅｓｏｆｔｈｅｃｒｕｓｔａｎｄｕｐｐｅｒｍａｎｔｌｅｏｆｔｈｅＴｉａｎｓｈａｎａｒｅａ￥ＹｉＸＵ；Ｊｉｅ－ＳｈｏｕＺＨＵ；Ｚｈｉ－ＪｉａｎＬＩＵ；Ｈｕａ－ＱｉｎｇＺＨＡＮＧａｎｄＹａ...     

On the hydro－spectrum of deep wells and the response ability of well－aquifer system

Ｏｎｔｈｅｈｙｄｒｏ－ｓｐｅｃｔｒｕｍｏｆｄｅｅｐｗｅｌｌｓａｎｄｔｈｅｒｅｓｐｏｎｓｅａｂｉｌｉｔｙｏｆｗｅｌｌ－ａｑｕｉｆｅｒｓｙｓｔｅｍＷｅｎ－ＢｉｎＪＩＡＮ（简文彬）；Ｂａｏ－ＲｅｎＣＨＥＮ（陈葆仁）ａｎｄＳｈｕ－ＹｕｎＬＩＵ（刘淑芸）（Ｄｅ...     

Research on the seismogenic environment for deep earthquake and the cause of earthquakes in Xinjiang and its adjacent areas

ＲｅｓｅａｒｃｈｏｎｔｈｅｓｅｉｓｍｏｇｅｎｉｃｅｎｖｉｒｏｎｍｅｎｔｆｏｒｄｅｅｐｅａｒｔｈｑｕａｋｅａｎｄｔｈｅｃａｕｓｅｏｆｅａｒｔｈｑｕａｋｅｓｉｎＸｉｎｊｉａｎｇａｎｄｉｔｓａｄｊａｃｅｎｔａｒｅａｓＱｉａｎｇＬＩ（李强）；Ｒｕｉ－Ｆｅｎｇ...     

Characteristic of crustal structure in the Shulu fault basin and its vicinity

（王椿镛，张先康，林中洋，李学清）ＣｈａｒａｃｔｅｒｉｓｔｉｃｏｆｃｒｕｓｔａｌｓｔｒｕｃｔｕｒｅｉｎｔｈｅＳｈｕｌｕｆａｕｌｔｂａｓｉｎａｎｄｉｔｓｖｉｃｉｎｉｔｙ￥Ｃｈｕｎ－ＹｏｎｇＷＡＮＧＩ；Ｘｉａｎ－ＫａｎｇＺＨＡＮＧ；Ｚｈｏｎｇ－ＹａｎｇＬ...     

Episodes and ages of seismic landslides along the Changma fault zone

ＥｐｉｓｏｄｅｓａｎｄａｇｅｓｏｆｓｅｉｓｍｉｃｌａｎｄｓｌｉｄｅｓａｌｏｎｇｔｈｅＣｈａｎｇｍａｆａｕｌｔｚｏｎｅＬａｉ－ＸｕｎＫＡＮＧ；（康来迅）ａｎｄＪｉａｎ－ＲｏｎｇＷＡＮＧ（王建荣）（ＥａｒｔｈｑｕａｋｅＲｅｓｅａｒｃｈＩｎｓｔｉｔｕｔｅｏ...     

Grouping occurrences being the fundamental feature of the strong earthquakes in Chinese mainland

ＧｒｏｕｐｉｎｇｏｃｃｕｒｒｅｎｃｅｓｂｅｉｎｇｔｈｅｆｕｎｄａｍｅｎｔａｌｆｅａｔｕｒｅｏｆｔｈｅｓｔｒｏｎｇｅａｒｔｈｑｕａｋｅｓｉｎＣｈｉｎｅｓｅｍａｉｎｌａｎｄＱｉｎ－ＺｕＬＩ（李钦祖）；Ｌｉ－ＭｉｎＹＵ（于利民）；Ｊｉ－ＹｉＷＡＮＧ（王吉易...     

Analysis of foreshock sequence of the 1975 Haicheng earthquake of Ms 7.3

Ａｎａｌｙｓｉｓｏｆｆｏｒｅｓｈｏｃｋｓｅｑｕｅｎｃｅｏｆｔｈｅ１９７５ＨａｉｃｈｅｎｇｅａｒｔｈｑｕａｋｅｏｆＭｓ７．３Ｚｈａｏ－ＲｏｎｇＺＵＯ（左兆荣）；Ｊｉａｎ－ＰｉｎｇＷＵ（吴建平）ａｎｄＺｈｉ－ＬｉｎｇＷＵ（巫志玲）（Ｉｎｓｔｉｔｕｔｅｏｆ...     

The application of seismic data with different precision in the determination of seismicity parameters

ＴｈｅａｐｐｌｉｃａｔｉｏｎｏｆｓｅｉｓｍｉｃｄａｔａｗｉｔｈｄｉｆｆｅｒｅｎｔｐｒｅｃｉｓｉｏｎｉｎｔｈｅｄｅｔｅｒｍｉｎａｔｉｏｎｏｆｓｅｉｓｍｉｃｉｔｙｐａｒａｍｅｔｅｒｓＸｕｅ－ＳｈｅｎＪＩＮ（金学申）；Ｙｉｎｇ－ＨｕａＤＡＩ（戴英华）；Ｊｕ...     

Lyapunov exponent and dimension of the strange attractor of elastic frictional system

ＬｙａｐｕｎｏｖｅｘｐｏｎｅｎｔａｎｄｄｉｍｅｎｓｉｏｎｏｆｔｈｅｓｔｒａｎｅａｔｔｒａｃｔｏｒｏｆｅｌａｓｔｉｃｆｒｉｃｔｉｏｎａｌｓｙｓｔｅｍＺｈｉ－ＲｅｎＮＩＵ（牛志仁）ａｎｄＤａｎｇ－ＭｉｎＣＨＥＮ（陈党民）（ＳｅｉｓｍｏｌｏｇｉｃａｌＢｕｒ...     

Changes in source parameters of foreshocks and aftershocks of the 2001 M_S=6.0 Yajiang, Sichuan, earthquake

Introduction An MS=6.0 earthquake occurred on February 23, 2001 in Yajiang county, Sichuan Province. The earthquake is located on the east of the southeast segment of the Litang-Dewu fault with strike of NW. Before the event, on February 14, an MS=5.0 earthquake took place nearly in the same place. In 1948 an MS=7.3 earthquake occurred on the northwestern segment of the Litang fault. The length of the surface rupture belt caused by the earthquake is 70 km, which extended from Litang to…     

1976年松潘地震序列的小震震源机制

利用区域地震台网的地震波资料，由垂直记录Ｐ和Ｓ振幅比值的拟合，反演得到松潘地震序列１５８个中小余震的震源机制解。分析表明虽然小震机制解的空间取向比较离散，但其优势取向和区域应力场相符。集中在３个地点和８８个小震机制解与离散分布的全区的７０个小震机制解之间没有显著差异，据此推论序列中３次大震之所以具有较大的逆冲滑动分量，系予存软弱面空间取向决定，而非应力场的原因。序列中的中小余震并没有表现出逆冲滑动     

2020年7月12日唐山古冶MS 5.1地震震源参数

利用河北及邻区地震台网提供的震相观测报告,使用双差定位方法,对2020年7月12日唐山古冶M_S 5.1地震序列进行重新定位,并基于部分地震台站记录的波形资料,采用近震全波形方法,反演得到主震震源机制解。精定位结果显示,此次地震序列展布长度约8 km,余震自主震位置向SW扩展,震源深度优势分布范围在10—18 km,发震断层面较陡,倾向SE。震源机制解显示,主震为一次走滑型事件,结合序列展布形态和地震活动背景,SW—NE向近似直立节面为可能发震断层面,与1976年唐山M_S 7.8主震断层特征基本一致。综上所述,古冶M_S 5.1地震为唐山M_S 7.8地震的又一次余震,属唐山老震区正常地震活动。     

Comparative Study of Changes in Stress-drop of the Jinggu MS6.6 and Ludian MS6.5 Earthquake Sequences

The earthquake stress-drop values of two sequences were accurately calculated after taking away the effects due to regional earthquake anelastic attenuation and station site response, using waveform data and seismic phase data of sequences of the Jinggu M_S6.6, and Ludian M_S6.5 earthquakes in Yunnan. These results show that the stress drop with magnitude increases within the scope of this study of magnitude. After eliminating the influence of the magnitude, the average value of stress-drop in the Jinggu sequence is higher than that of the Ludian sequence at the same magnitude range. This may be related to the stress state in different regions. In terms of the changes of time and space of stress-drop, before M_S5.8 strong aftershock, the stress-drop is "slowing down-turning up-keeping a high value" after the mainshock, meanwhile, almost all of the abnormally high stress drop value is distributed around the M_S5.8 strong aftershock, showing that the stress environment in the region was increasing after the mainshock. And after the M_S5.9 strong aftershock, stress-drop rapidly declines to a relatively stable state, meanwhile, the high value of stress-drop is distributed around the strong aftershock, showing that the regional tectonic stress gets more fully release, its stress environment begins to rapidly decrease. For the Ludian sequence without a strong aftershock occurring, the average value of stress drop is lower than that of the Jinggu earthquake sequence at the same magnitude range, while at the same time, the stress-drop of the aftershock sequence almost hasn''t changed much. In the time after the mainshock, combined with the release characteristics of the main energy, the stress in the region is excessively released, the subsequent stress in the region gradually returns to normal. This may be the reason why the activity of Ludian aftershocks significantly was weaker and subsequently there were no strong aftershocks occurred.     

2001年四川雅江6级地震的前震与余震震源参数的变化h

研究了2001年2月四川省雅江县发生的MS5.0前震、MS6.0主震及序列地震的震源机制、波谱参数及应力降的变化过程与震区地震活动．根据雅江地震的震源机制解，并结合余震空间分布图象分析，选雅江5.0级的节面Ⅰ为推测的地震断层，走向NNE；选雅江6.0级地震的节面Ⅱ为推测的地震断层，走向WNW，分析前震与主震的断层面走向是斜交的．雅江6.0级地震发生前震区应力降水平有所增加，这一现象与震区地震活动的增加是一致的．雅江地震序列的衰减起伏过程, 前、余震波谱变化, 以及震源力学错动机制等均呈现复杂特征．      

1976年唐山MS7.8地震余震序列持续时间及对地震危险性分析的意义

1976年7月28日唐山MS7.8大地震对唐山及其周边地区造成了重大的人员伤亡和财产损失. 主震之后约15小时滦县又发生了MS7.1地震; 同年11月15日宁河也发生了MS6.9地震. 唐山MS7.8主震后的余震一直持续至今,使该区域至今保持了与主震前相比具有较高的地震活动性．如何估计余震的持续时间,并进一步将余震从主震目录中去除,一直是地震学中所关注的问题．该文通过对数线性回归和理论计算,从不同角度求取并讨论了1976年唐山MS7.8大地震的余震持续时间．结果表明,由对数线性回归计算得到的余震持续时间约为80 a．而基于Dieterich的余震触发理论所得到的余震持续时间则与区域剪应力变化率有关．区域剪应力变化率可有几种不同方法求得: ① 根据剪应力变化率和静态应力降Delta;tau;e及地震回复周期tr之间的关系求取应力变化率,该方法所得到的余震持续时间约为70——100 a;② Ziv和Rubin对Dieterich的方法进行了修正,给出了通过远场加载速率和断层宽度求取应力变化率, 该方法得到的余震持续时间约为80 a;③ 由背景场地震活动性求取远场剪应力速率, 可以得到该地区二维分布式的余震持续时间,此方法得到的研究区域内余震持续时间为130——160 a．综上,唐山地区余震持续时间约为70——140 a,据此, 该地区现今所发生的地震仍为MS7.8唐山地震所触发的余震．      

Relationship between the earthquake sequences of Tangshan and Xingtai and the three dimensional velocity structure

In this paper, based on the results of tomographic image of Tangshan and Xingtai areas, the relations between the characteristics of the two strong earthquake sequences and their three-dimensional velocity structures are studied. The research results indicate that:① Mosaic distribution of low-velocity bodies and high-velocity bodies, especially the existence of high-velocity bodies with large size in crust are the common basis of development of the two earthquake sequences. ②Scale, depth, and heterogeneity of high-velocity and low-velocity bodies are the important factors to effect the characteristic of earthquake sequences.③ The depth of the high-velocity body in Tangshan area is less than that in Xingtai area, which is the principal reason why the dominant focal depth and the biggest focal depth of Tangshan earthquake sequence are less than Xingtai's.④The depth of the high-velocity bodies in Ninghe area is more than that in Tangshan-Luanxian area, which lead to the biggest magnitude and epicentral intensity are lower. These results could be helpful for predicting the main shock of strong swarm-type earthquakes and later strong aftershocks.     

1950年西藏察隅M8.6强震序列震源参数复核

1950年8月15日西藏察隅发生M8.6巨大地震.我们利用收集到的全球239个台站的P波资料,利用我国国家测震台网的常规定位方法和模型,对察隅M8.6强震序列进行了重新定位,并在此基础上重新计算了震源机制解.重定位后的结果表明,察隅M8.6强震序列显示出不同时段的震中分区分布特征:第1阶段是前震,1950年2月23日在墨脱北部雅鲁藏布江大拐弯的顶部发生;第2阶段是1950年8月15日─1950年8月18日,发生主震和之后3天内的余震,都分布在察隅附近,并且这些震中呈北西条带分布;第3阶段的余震是1950年8月22日─1950年9月13日,它们扩展到南部的印度和缅甸地区;第4阶段的余震是1950年9月30日─1951年4月15日,发生在西部的墨脱、错那等地.这四个分区的关联特点为顺时针旋移.重新计算后的震源机制解显示出:主震的NWW走向的节面与主震后2区内余震震中的NWW分布方向一致;序列中所有的压应力轴P和张应力轴T,都接近于水平向,其倾伏角大都小于20°;察隅主震和2区内余震的压应力轴P为近南北向,张应力轴T为近东西向;但3区和4区余震的P轴为近东西向,T轴为近南北向.反映出该强震序列中余震震源机制解的差异比较大.     

2013年芦山地震序列震源机制与震源区构造变形特征分析

基于四川区域地震台网记录的波形资料,利用CAP波形反演方法,同时获取了2013年4月20日芦山M7.0级地震序列中88个M≥3.0级地震的震源机制解、震源矩心深度与矩震级,进而利用应变花（strain rosette）和面应变（areal strain）As值,分析了芦山地震序列震源机制和震源区构造运动与变形特征.获得的主要结果有：（1）芦山M7.0级主震破裂面参数为走向219°/倾角43°/滑动角101°,矩震级为M_W6.55,震源矩心深度15 km.芦山地震余震区沿龙门山断裂带走向长约37 km、垂直断裂带走向宽约16 km.主震两侧余震呈不对称分布,主震南西侧余震区长约27 km、北东侧长约10 km.余震分布在7~22 km深度区间,优势分布深度为9~14 km,序列平均深度约13 km,多数余震分布在主震上部.粗略估计的芦山地震震源体体积为37 km×16 km×16 km.（2）面应变As值统计显示,芦山地震序列以逆冲型地震占绝对优势,所占比例超过93%.序列主要受倾向NW、倾角约45°的近NE-SW向逆冲断层控制;部分余震发生在与上述主发震断层近乎垂直的倾向SE的反冲断层上;龙门山断裂带前山断裂可能参与了部分余震活动.P轴近水平且优势方位单一,呈NW-SE向,与龙门山断裂带南段所处区域构造应力场方向一致,反映芦山地震震源区主要受区域构造应力场控制,芦山地震是近NE-SW向断层在近水平的NW-SE向主压应力挤压作用下发生逆冲运动的结果.序列中6次非逆冲型地震均发生在主震震中附近,且主震震中附近P轴仰角变化明显,表明主震对其震中附近局部区域存在明显的应力扰动.（3）序列整体及不同震级段的应变花均呈NW向挤压白瓣形态,显示芦山地震震源区深部构造呈逆冲运动、NW向纯挤压变形.各震级段的应变花方位与形状一致,具有震级自相似性特征,揭示震源区深部构造运动和变形模式与震级无关.（4）不同深度的应变花形态以NW-NWW向挤压白瓣为优势,显示震源区构造无论是总体还是分段均以NW-NWW向挤压变形为特征.但应变花方位与形状随深度仍具有较明显的变化,可能反映了震源区构造变形在深度方向上存在分段差异.（5）芦山地震震源体尺度较小,且主震未发生在龙门山断裂带南段主干断裂上,南段长期积累的应变能未能得到充分释放,南段仍存在发生强震的危险.     

A possible change in stress field orientation due to the 1976 Tangshan earthquake

Two techniques are used to study the stress field in the Tangshan region. First, the mean directions of principal stress axes in three subregions of the Tangshan aftershock region are determined from 29 focal mechanism solutions. In doing so a slip-fitting technique is applied which determines the mean stress tensor by minimizing the angle between the observed slip direction on every fault plane and the calculated shear stress resolved onto the fault planes. Each of the two nodal planes of the focal mechanism solutions are alternately considered as a possible fault plane. Second, by making a grid search over all possible orientations of stress axes, the meanP,B andT axes in the Tangshan region, both before and after the Tangshan mainshock, are found on the basis of firstP-wave polarity readings from a number of small earthquakes. The results indicate that there is a possible azimuthal change of the principal stress axes in the focal region due to the occurrence of the mainshock.