1995年日本兵库县南部地震时淡路岛上出现的地震断层的形态特征

1995年日本兵库县南部地震时在淡路岛上出现的地表地震断层主要由三条地表破裂带组成、野岛地震断层、松帆地震层和楠本地震断层。野岛地震断层从淡路岛北端的淡路町住西南延伸到一宫町的尾崎,长达18km,其北段沿着早期存在的野岛断层分布,而南段则作为新断层出现,野岛地震断层的断层的北段主要由一些相互平行或次平行的右列剪切断层和许多左列和性裂隙组成,其南段则是由集中在十多米宽的大量不连续的地表破裂带所组成。野岛地震断层一般走向N30°～60°E倾向SE,地貌错位和断层擦痕均显示出此断层为一具有逆断层性质的右旋走滑断层,沿一些主要露头测定的北段水平位移量一般为100～200cm,垂直位移量为5O～100cm;而南段的水平、垂直位移量均只有几厘米至20cm。最大位移量在平林断层崖测得;水平180cm、垂直l30cm、实际位移量2l5cm。松帆地震断层走向N40°～60°W,沿着淡路岛北端部的海岸线分布,长达约1km。楠本地震断层沿早期存在的楠本断层出现,分布于淡路岛东北部的海岸边上,走向N35°～6O°W倾向NW 。根据地表地震断层的形态及地貌错位特征,野岛地震断层可被分为四条断层段,并在形态上呈现右列。地质和地貌证据以及余震分布的特征清楚地表明这4条断层段的几何形态和分布特征是受早期存在的地质构造所控制的,同时也说明了地震断层的破裂过程具有拉分(pulling-apart)和推隆(pushing－up)的过程,这两个过程分别产生了张性裂隙、拉分盆地、逆断层和挤压隆起等构造。     

2005年1月18日乳山ML4.3地震序列

对2005年1月18日乳山ML4.3地震序列特征及烈度分布进行了介绍, 认为乳山ML4.3地震序列是一次能量衰减较快、频度起伏衰减的主-余型地震序列, 序列本身不具有明显的前兆意义.     

A new approach of selecting real input ground motions for seismic design: The most unfavourable real seismic design ground motions

This paper presents a new way of selecting real input ground motions for seismic design and analysis of structures based on a comprehensive method for estimating the damage potential of ground motions, which takes into consideration of various ground motion parameters and structural seismic damage criteria in terms of strength, deformation, hysteretic energy and dual damage of Park & Ang damage index. The proposed comprehensive method fully involves the effects of the intensity, frequency content and duration of ground motions and the dynamic characteristics of structures. Then, the concept of the most unfavourable real seismic design ground motion is introduced. Based on the concept, the most unfavourable real seismic design ground motions for rock, stiff soil, medium soil and soft soil site conditions are selected in terms of three typical period ranges of structures. The selected real strong motion records are suitable for seismic analysis of important structures whose failure or collapse will be avoided at a higher level of confidence during the strong earthquake, as they can cause the greatest damage to structures and thereby result in the highest damage potential from an extended real ground motion database for a given site. In addition, this paper also presents the real input design ground motions with medium damage potential, which can be used for the seismic analysis of structures located at the area with low and moderate seismicity. The most unfavourable real seismic design ground motions are verified by analysing the seismic response of structures. It is concluded that the most unfavourable real seismic design ground motion approach can select the real ground motions that can result in the highest damage potential for a given structure and site condition, and the real ground motions can be mainly used for structures whose failure or collapse will be avoided at a higher level of confidence during the strong earthquake. Copyright © 2007 John Wiley & Sons, Ltd.     

2020年2月18日长清MS4.1地震发震构造研究

本文利用基于波形互相关的双差定位方法对2020年2月18日长清M_S4.1地震序列进行了精定位计算, 共得到33个地震事件的精定位结果。 结果显示, 地震序列主要沿NW向分布, 在水平方向上具有自NW向SE迁移, 在深度上具有由浅向深迁移的特征; 序列震源深度主要集中在2~7 km, 其中, 主震的震源深度约2.8 km。 由于长清地震序列的地震数量较少, 为了更准确地了解长清地震序列的发震构造、 探索该序列的发生和发展过程, 本文采用CAP方法反演了主震的震源机制解, 其中, 节面Ⅰ走向223°、 倾角42°、 滑动角-160°, 节面Ⅱ走向117.9°、 倾角76.8°、 滑动角-49.8°, 最佳拟合震源矩心深度约2.8 km, 矩震级M_W4.2。 结合区域构造特征分析认为, 长清M_S4.1地震的发震断裂为孝里铺断裂和东阿断裂之间发育的一条浅层次生断裂。 在ENE向区域应力场作用下, 发震断裂产生高角度正断滑动, 并伴有左旋走滑分量, 从而引发长清地震序列。     

伽师强震群震源特征及震源机制力学成因分析

应用改进的主地震相对定位法对17年伽师强震群3级以上地震进行了精确定位,根据较强地震的空间分布和震源机制解推断出伽师震群的发震构造为北北西向的雁行断裂.根据伽师震群地震的2177个P波初动方向记录,计算了伽师震群的平均震源机制解.基于Silver的震源模型,由震源谱推断了伽师震群主要地震的破裂方向,破裂尺度及应力降.文中最后用右阶雁行断裂的数值模型计算了伽师震群的发震构造所产生的扰动应力场的空间分布图像,用其解释了序列地震震源机制的多样性和低应力降现象,并认为特定的雁行发震构造与强震的多发性有关.     

Causes of rockfalls in Al-Huwayshah area,Yemen

According to topography of Yemen,most areas and villages are located at obligated crest,toe of mountain and under cliffs.Therefore Al-Huwayshah consisting of Tawilah sandstone group is characterized by steep slope reach to 90° in some areas.This area is affected by strong tectonic movements and faults that occurred during the geological epochs.This effect enhances to find out fractures and joints as well as the rocks become brittle and ready to slide depending on the position of area.And there are some frac...     

2021年四川泸县M6.0地震发震机理及地震活动时空演化特征

2021年9月16日四川泸县发生M6.0地震, 该地震发震构造不明, 发震机理尚存在争议.地震精定位和震源机制有助于分析地震活动时空演化与震源破裂特征, 能够有效揭示活动构造机制和地震发生机理, 为评估区域地震危险性提供科学依据.为此, 本文首先采用双差定位法对震中及附近2009年1月至2021年10月发生的地震进行了精定位, 结果显示, 研究区地震震源深度大多集中在10 km范围内, 事件主要沿地表断层呈条带状或丛集分布, 部分震群邻近当地工业井, 周边无明显断层分布.其次, 通过CAP波形反演计算得到M≥3.5地震的震源机制解, 表明研究区震源破裂以逆冲挤压型为主, 部分震源机制解具有不确定性.基于震源机制解反演区域应力场, 进一步探讨了区域应力场与地震事件的力学一致性.研究结果显示, 区域应力场以水平构造挤压作用为主, 部分事件震源机制解与其吻合度较低, 暗示存在局部应力差异.综合地震活动时空演化特征、已知断层展布以及区域应力场等研究结果, 认为华蓥山断裂带南段的地震活动与资源开采活动密切相关, 泸县M6.0地震是在局部应力场扰动下, 下方滑脱层活动触发了上覆隐伏断层的挤压错动而产生.

     

澜沧—耿马地震的震源机制研究

本文利用中国数字化地震台网（CDSN）记录的2°—40°范围内的长周期P波垂直分量波形资料,通过理论地震图拟合的方法,研究了1988年云南澜沧—耿马地震主震及两个余震的震源机制.结果表明,主震由三个震源机制不尽相同的子事件组成.第一个子事件的震源机制为:走向N30°W,倾角88°,错动角185°,地震矩为0.55×1020Nm.第二个子事件的震源机制为:走向N33°W,倾角90°,错动角209°,地震矩0.24×1020Nm,延迟时间为25s.第三个子事件的震源机制为:走向N65°W,倾角82°,错动角172°,地震矩为0.14×1020Nm,延迟时间为70s.这种在空间上相距甚小而在时间上有分离、子事件的震源机制相差较为显著的复杂震源过程,与现场综合考察所见的地表裂缝分布一致,可以解释为单一裂缝的X型共轭剪切破裂,两个余震震源机制均为:走向N10°W,倾角86°,错动角185°,地震矩分别为0.54×1018Nm和4.29×1018Nm.     

Epicenter and magnitude of large earthquake determined from high-rate GPS observations: A case study of the 2008 M8.0 Wenchuan earthquake

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.