邢台地震区大地电磁观测与研究

在邢台地震区进行了大地电磁观测,并对该地区电性结构与地震的关系进行了研究.该地区地下电性结构较复杂,电性在纵向及横向都存在着显著的变化.一维结果表明,该地区电性纵向分布可分五层,第三层为高导层,埋深约10-20 km.在地震震源集中区,高导层深度有较大变化.电性横向分布也有明显变化.总体上看,地震区内电阻较高,可是地震并不发生在电阻率最高的地点,而多发生在电性变化较大地段.     

邢台地震区大地电磁观测与研究

在邢台地震区进行了大地电磁观测,并对该地区电性结构与地震的关系进行了研究.该地区地下电性结构较复杂,电性在纵向及横向都存在着显著的变化.一维结果表明,该地区电性纵向分布可分五层,第三层为高导层,埋深约10—20 km.在地震震源集中区,高导层深度有较大变化.电性横向分布也有明显变化.总体上看,地震区内电阻较高,可是地震并不发生在电阻率最高的地点,而多发生在电性变化较大地段.     

东南沿海地震区地震活动特性与未来趋势分析

根据地震资料，对东南沿海地震区地震活动特下及未来趋势进行了初步分析与研究，结果表明：（１）从地震活动轮回分析，东南沿海地震区从１９５９年开始的第五个轮回中的地震活动时段，估计将延续到２０３１年前后结束，而后转入本轮回的平静时段；（２）２０００年以前，研究区有可能发生１次Ｍｓ≥６．０地震，到２００５到则最多发生２次；（３）东南沿海地震区下一次发生Ｍｓ≥６．０地震的地区可能在河源－邵武地震带上，尤其可     

福建东部地区大地电磁测深研究

1986年至1987年我们在福建东部做了深部大地电磁测深,取得以下主要结果: 1.福州、漳州两地区存在上地幔软流层的隆起（底辟）,岩石层变薄,并有次级底辟发育于20-30km深度,说明地幔热活动强烈,两地热田有深部热背景. 2.惠安至龙海一线大致呈北60°东为一低阻断面,该断面的地下电性结构和洋壳地电结构相似,推测该断面是向上仰冲的古洋壳与陆缘的缝合线. 3.永春、同安地区壳内高导层埋深明显比其它地区浅,是有希望的地热远景区,需进一步做工作.     

福建东部地区大地电磁测深研究

1986年至1987年我们在福建东部做了深部大地电磁测深,取得以下主要结果: 1.福州、漳州两地区存在上地幔软流层的隆起（底辟）,岩石层变薄,并有次级底辟发育于20—30km深度,说明地幔热活动强烈,两地热田有深部热背景. 2.惠安至龙海一线大致呈北60°东为一低阻断面,该断面的地下电性结构和洋壳地电结构相似,推测该断面是向上仰冲的古洋壳与陆缘的缝合线. 3.永春、同安地区壳内高导层埋深明显比其它地区浅,是有希望的地热远景区,需进一步做工作.     

闽粤沿海全新世垂直构造运动的速率

基于华南地区新构造运动具有断块垂直差异运动的特征,本文主要根据目前已测定的,分布于闽粤沿海地区的若干个全新世海相沉积物的放射性年代,海拔高度等数据,初步估算和对比闽粤沿海不同断块构造区的垂直构造运动的速率,并探讨它与地震活动的关系     

闽粤台沿海北西西向最新构造带与大震构造背景

闽粤台沿海自台湾运动以来逐渐形成了多条北西西向隆起—拗陷的最新活动构造带,与已知的北东—北北东向隆起、拗陷带构成了区域性镶嵌构造格局。 研究区内除板块相互碰撞、俯冲及上地幔物质上涌形成大震构造背景外,莫霍面隆起或隆起断距大、低速层厚、地壳变薄、近两、三千年地表抬升差异活动显著以及台东近海有北西西向构造活动等,也都是发生大震的重要构造背景     

FEATURES OF TECTONIC LANDFORM OF FAULT BLOCKS IN SOUTH CHINA COASTAL AREA

In this paper, the South China coastal area is divided into several fault block areas (first class), sub-areas (second class) and mini-areas (third class) based on their dynamic signs, heridity, uniformity, paricu-larity and the mode of action of tectonic stress. Their tectonic geomorphological features are elaborated and the amplitude as well as the rate of relative motion since the end of the late Pleistocene epoch are estimated from 14C data of the samples which fundamentally repres     

辽东半岛沿海地区海岸地貌及其所反映的新构造运动

本文根据辽东半岛沿海126条海岸阶地剖面资料统计出区内各类海岸地貌的级数和高度,作者认为:海积地貌面主要是全新世中期形成的;Ⅰ—Ⅴ级海蚀阶地是更新世各期形成的。通过海岸阶地纵剖面分析了本区新构造运动,提出了金州断裂和鸭绿江断裂是本区主要的活动断裂。作者还指出本区的海岸阶地与下辽河盆地的海侵层可能具有成因联系,并据此定量地分析了它们间的相对运动     

A STUDY OF SALT WATER ENCROACHMENT IN THE COASTAL AQUIFER AT DIGHA,MIDNAPORE DISTRICT,WEST BENGAL,INDIA

Synopsis

Between 1963 and 1965, sinking of anger boreholes and testing of quality of groundwater at different depths along Digha coast provided the principal basis for defining the distribution and movement of the saline and fresh groundwater within a phreatic aquifer (7–9 metres in thickness) consisting of fine to coarse grained sand with occasional soft clay lenses of Recent age. The auger holes were sunk along 10 selected lines in an area of about 25 sq.km. extending from 3 km east of Digha on the east to the confluence of the Subarnarekha river with the Bay of Bengal on the west.

The results of the study revealed the existence of a fresh water wedge (chloride content varying from 20 to 300 ppm) separated by two saline water zones, one near the top and the other at the bottom of the aquifer. Isochlor of 500 ppm and 2.3 chloride-bicarbonate ratio delineated the saline groundwater body. The 300 and 500 ppm isochlors defined the zone of diffusion which had a variable shape and thickness depending on several factors.

Minor movements of the interface occur due to tidal and groundwater recharge variations. The interface was found to occur at much shallower depth than that calculated on the basis of the Ghyben-Herzberg principle. The reasons for such deviation have been discussed.     

甘肃东部及邻区地壳Qp值分布特征

本文使用兰州遥测地震台网有数字波形记录的12个台站记录到的83个近震P波资料,应用波谱计算Q_P值的频率域方法,求得甘肃东部及邻区Q_P值在170—1300之间。通过分析发现低Q_P区小震活动密集,中强地震较多;高Q_P区地震活动最弱;在高Q_P区和低Q_P区的边界一带,是历史和现今6级以上破坏性地震发生区。文中最后应用组合模式,对Q_P值的分布进行了分析,并对甘肃东部某些地区的地震危险性作了估计。     

内蒙古东部地区地震活动演化特征

通过对内蒙古东部中等地震的有序分布、中等地震密集增强、地震从集、空区和条带及显著地震及中强地震迁移背景方面的演化特征研究,分析认为,阿巴嘎旗及邻区、扎兰屯-牙克石、呼伦贝尔-兴安盟-锡盟-通辽交界地区将是未来中强地震的可能区域。通过对2003年8月-2006年3月间发生在东部的中强地震沿大兴安岭对迁特征研究,综合认为,内蒙古东部已成为东北地区中强地震活动主体地区。     

河西走廊东部地区地壳下部异常低阻层的发现

1979—1981年我们完成了河西走廊东部张掖—武威一带的大地电磁测深野外探测。经过室内资料处理,发现走廊盆地下部地壳内普遍存在一异常低阻层。张掖—民乐盆地和武威盆地内的五个测点对这一低阻层都有明显地显示,这些测点的位置及其编号如图所示。     

东南沿海地震带（含台湾海峡地区）地震活动期的讨论

东南沿海地震带（含台湾海峡地区）地震活动存在一个３４０年左右的主要分期，目前处在１４００年以来的第二活动期。本文充分注意到７０余年的次级分期影响，分析表明，第二活动期可以简单划分为平静和释放两个阶段，释放阶段存在两个应变释放高潮时段自１９８６年进行第二高潮时段，１９９４年９月台湾海峡７．３级地震其主要标志之一，预计这一高潮时段将持续至２０４０年左右，其间可能会有效次Ｍ≥６级地震发生，并且不能排除继     

福建省龙海—漳浦沿海第四纪地壳运动特征与地震

本文论述了福建龙海—漳浦沿海地区的第四纪地层及沉积结构、构造地貌、第四纪地壳运动特征及其与地震活动的关系。     

巴基斯坦沿海地区地震危险性分析

通过确定性和概率性方法，对发展迅速的巴基斯坦沿海地区进行了地震危险性评估．根据该地区的地震构造和地质条件，确定了5个地震区域的11个断层作为该地区的潜在震源，计算了每个潜在震源的最大可能震级．根据与之相关震源的最大可信震级，计算了7个沿海城市的峰值加速度（PGA）．瓜达尔（Gwadar）和奥尔马腊（Ormara）的峰值加速度分别为0.21和0.25 g，处于地震危险性水平较高的地区；杜尔伯德（Turbat）和卡拉奇（Karachi）位于地震危险性水平较低的地区，峰值加速度小于0.1 g．同时，分别绘制了50年和100年超越概率为10％的PGA区划图，区划图的分区间隔为0.05 g．      

CHARACTERISTICS OF FOCAL MECHANISMS AND STRESS FIELD IN THE EASTERN BOUNDARY OF SICHUAN-YUNNAN BLOCK AND ITS ADJACENT AREA

This study is devoted to a systematic analysis of the stress state of the eastern boundary area of Sichuan-Yunnan block based on focal mechanisms of 319 earthquakes with magnitudes between M3.0 and M6.9, occurring from January 2009 to May 2018. We firstly determined the mechanism solutions of 234 earthquakes by the CAP method, using the broadband waveforms recorded by Chinese regional permanent networks, and collected 85 centroid moment tensor solutions from the GCMT. Then we investigated the regional stress regime through a damp linear inversion. Our results show that:1)the focal mechanisms of moderate earthquakes are regionally specific with three principal types of focal mechanisms:the strike-slip faulting type, the thrust faulting type and the normal faulting type. The strike-slip faulting type is significant in the eastern boundary area of Sichuan-Yunnan block along the Xianshuihe-Xiaojiang Fault, the Daliangshan Fault, and the Zhaotong-Lianfeng Fault. The thrust faulting type and the combined thrust/strike-slip faulting type are significant along the Mabian-Yanjin Fault, Ebian-Yanfeng Fault and the eastern section of Lianfeng Fault; 2)The most robust feature of the regional stress regime is that, the azimuth of principal compressive stress axis rotates clockwise from NWW to NW along the eastern boundary of Sichuan-Yunnan Block, and the clockwise rotation angle is about 50 degrees. Meanwhile, the angels between the principal compressive axis and the trend of eastern boundary of Sichuan-Yunnan Block remain unchanged, which implies a stable coefficient of fault friction in the eastern boundary fault zone of Sichuan-Yunnan Block. The movement of the upper crust in the southeastern Tibetan plateau is a relatively rigid clockwise rotation. On the whole, the Xianshuihe-Xiaojiang Fault is a small arc on the earth, and its Euler pole axis is at(21°N, 88°E). The Daliangshan Fault is surrounded by the Anninghe-Zemuhe Fault, which formed a closed diamond shape. When the Sichuan-Yunnan block rotates clockwise, the Daliangshan Fault locates in the outer of the arc, while the Anninghe-Zemuhe Fault is in the inward of the arc, and from the mechanical point of view, left-lateral sliding movement is more likely to occur on the Daliangshan Fault. Our results can be the evidence for the study on the "cut-off" function of the Daliangshan Fault based on the stress field background; 3)The regional stress regime of the eastern boundary faults zone of the Sichuan-Yunnan Block is the same as the south section of the Dalianshan Fault, and the focal mechanism results also reveal that the Dalianshan Fault is keeping left-lateral strike-slip. There may be the same tectonic stress field that controls the earthquake activities in the southern section of Daliangshan Fault and Zhaotong-Lianfeng Fault. The regional stress regime of Zhaodong-Lianfeng Fault is also the same with the Sichuan-Yunnan Block, which implies that the control effect of the SE movement of the Sichuan-Yunnan block may extend to Weining.     

渭河盆地东部地区的活断层

本文根据近年来的调查结果,讨论了渭河盆地东部地区六条主要断裂的活动情况。指出这些断裂现今活动以倾向滑落为主,同时兼有一定分量的左旋走滑运动