四川普格县地震地质调查与活动断层分布特征

普格县活动断层及新构造作为则木河断裂带一个重要的组成部分,是普格县城区规划重点考虑的活动构造,通过初步分析该断层带的基本地质特征、活动性,为该区防震减灾规划及分析该断裂潜在地震危害性奠定了基础。通过遥感解译、地质测量、隐伏段电法、地球化学勘探等手段,综合地震地质调查、活动断层调查研究成果,编制工作区活动断层分布图,研究新构造展布及运动特征,分析新构造与地震活动的关系,初步分析其稳定性、危险性及危害性。

四川盆地南缘筠连-长宁地震区扎子坳断层探测及活动性初步研究

通过地震活动性调查、地表地震地质调查、浅层地震勘探、高密度电法勘探及探槽剖面分析等多种手段对扎子坳断层进行综合研究,结果发现,扎子坳断层发育于古生代二叠系砂岩和中生代三叠系灰岩、砂岩地层中,属逆断层,断层总体呈NNE向展布,长约15 km,破碎带影响宽度一般小于20 m,断层规模较小。结合浅层地球物理勘探和探槽剖面分析结果初步推测,扎子坳断层不具备晚更世晚期活动性,为2017-01-28筠连4.9级地震的发震构造。

高密度电法和地震映像在隐伏断裂中的应用——以玉林天然气支线项目为例

采用高密度电法和地震映像法的综合应用来勘探隐伏断裂带。首先,通过分析高密度电法和地震映像法得到的综合物探异常,进行钻探验证,来确定断裂带的具体位置;再结合地震地质调查,来确定隐伏断裂带的走向。最后,根据隐伏断裂带的具体位置和走向,来确定玉林天然气支线穿过隐伏断裂带的具体位置,为地震安全性评价提供了有利的依据,说明高密度电法和地震映像法勘探隐伏断裂的一致性。

综合物探方法在广西罗城县活动断裂鉴定中的应用

城市活动断层探测在城市发展建设过程中和保障人民生命财产安全方面起到重要作用。本文以鉴定罗城断裂和上天桥—寺门断裂活动性为目的,在地震地质调查确定其断裂的几何学、运动学和年代学的基础上,选择第四系覆盖断裂最有可能活动的地段,重点采用高密度电法和地震映像方法来探测断裂在隐伏地段的具体位置,通过排钻验证,以及揭露其断裂与第四纪覆盖层之间的错断关系,来确定其断裂最新活动年代。结果表明,高密度电法和地震映像综合物探方法准确探测到了罗城断裂和上天桥—寺门断裂在隐伏地段的位置,且钻孔岩心中断裂面、断裂擦痕、断裂碎裂岩和构造角砾岩等发育,但断裂未错断第四系覆盖层,从而确定其断裂活动年代为早更新世。根据相关规范要求,罗城断裂和上天桥—寺门断裂全新世以来不活动,罗城县的建设规划可不采取避让措施,该鉴定结果为今后罗城县的工程建设提供了安全保障。

Slope Seismic Response Monitoring on the Aftershocks of the Wenchuan Earthquake in the Mianzhu Section

Previous investigations have shown that the seismic response of slopes during the Wenchuan earthquake was highly variable. The present study tries to give an answer to the question： Which are the main factors affecting the seismic response degree of slopes？ With the support of the China Geological Survey Bureau, we set 3 monitoring sections in Jiulong slope, Mianzhu city, China with the aim to record the site response of the slope during the affershoeks of the Wenehuan earthquake. After the Wenchuan earthquake, which happened on 12 May 2008, 30 aftershocks have been recorded in these monitoring points. We analyzed 11 records, with magnitudes ranging from ML = 4.6 to ML = 3.1. The amplification factors of the horizontal compound PGA and 3D compound PGA have been determined for the 3 points at different elevations on the slope. Results showed that the dynamic response of the slope on the earthquake was controlled by factors such as topography and the thickness of the Quaternary overburden.

The Influence of Earth Temperature on the Dynamic Characteristics of Frozen Soil and the Parameters of Ground Motion on Sites of Permafrost

Earth temperature is one of the most important factors influencing the mechanical properties of frozen soil. Based on the field investigation of the characteristics of ground deformation and ground failure caused by the M S8 1 earthquake in the west of the Kunlun Mountain Pass, China, the influence of temperature on the dynamic constitutive relationship, dynamic elastic modulus, damping ratio and dynamic strength of frozen soil was quantitatively studied by means of the dynamic triaxial test. Moreover, the characteristics of ground motion on a permafrost site under different temperatures were analyzed for the four profiles of permafrost along the Qinghai Xizang(Tibet) Railway using the time histories of ground motion acceleration with 3 exceedance probabilities of the Kunlun Mountains area. The influences of temperature on the seismic displacement, velocity, acceleration and response spectrum on permafrost ground were studied quantitatively. A scientific basis was presented for earthquake disaster mitigation for engineering foundations, highways and underground engineering in permafrost areas.

Surface Rupture and Coseismic Displacement of the M_S7.1 Yushu Earthquake

On April 14, 2010, a devastating earthquake measured 7.1 on the Richter scale struck Yushu county, Qinghai Province, China. Field geological investigation and remote sensing interpretation show that this earthquake generated an inverse ＂L-shaped＂ surface rupture zone, approximately 50km long. The surface rupture zone can be divided into three segments. Between the northern and middle segments of the surface rupture, there is a 16km-long segment, where no rupture was observed. The middle and the southern segments are arranged in a left-step manner, and there are right-step en echelon ruptures developed in the stepovers. The seismogenic structure is the Yushu fault, which is dominated by strike-slip with a small amount of thrust component. The earthquake results from the differential movements between the southern Qiangtang Block and northern Bayan Har Block. The earthquake recurrence interval is 185a^108a. Along an approximately 20km-long part of the Garze-Yushu fault, between the southern surface rupture of Yushu Ms7. 1 earthquake and the 1896 earthquake, there is no surface rupture, its seismic risk needs further research.

Seismic Acquisition on the Buried-Hill Faulted Zone of the Jiyang Sag

The pattern of the subtle traps, in which oil and gas accumulated, in the buried-hill faulted zone in the Jiyang sag is very complicated, and very hard to prospect. The paper analyses the main difficulties in exploring the complicated buried-hill faulted zone of the area from a point of geology.The typical pattern of the buried-hill zone in the Jiyang sag is studied using the forward modeling.Target-orient layout design and full 3-D seismic technology, which are useful for oil and gas exploration on the zone, are put forward. Taking the exploration for oil and gas traps on the zone as an example, certain technologies and the effect of their applications about the design for target acquisition,acquisition on a wide-azimuth, point sources and point receivers are discussed.

The Recent Crustal Deformation on the Sichuan-Yunnan Rhombic Block Boundaries

Based on data from an across-fault survey along the Sichuan-Yunnan rhombic block boundaries, the recent deformation characteristics on each fault have been analyzed. It was found that the rate of crustal deformation is slowing down along the northern segment and increasing along the southern segment. Each fault has different features of deformation. The horizontal deformation is mainly characterized by left-lateral strike-slip. The rate of vertical deformation is less than that of the horizontal deformation. The faults have the feature of upper wall uplifting alternated with descending. The anomaly changes of crustal deformation at some sites are closely related to the seismicities near the sites.

Cluster of Strong Earthquakes and Aftershocks in Ahar-Varzeghan Area on August 11, 2012

Seismic events are very complex spatial-temporal phenomena. Seismic catalogues, reporting information about spatial-temporal distribution of the main shocks, are nowadays available for many seismic areas in the world, very often major events mark the beginning of a series of earthquakes （aflershocks） whose frequency and energy are meanly decreasing in time down to the background level of activity. Azerbaijan is one of the most active segments of the Alpine-Himalayan seismic belt and marks the junction between the African-Arabian and Indian plate to the south, and Eurasian plate to the north. The cluster of earthquakes that struck near Varzeghan-Ahar was centered near the Gosha-Dagh fault, but preliminary data suggested that the fault was not responsible for the temblor. On the late afternoon of Saturday, August 11, 2012, the northwest of Iran was shaken by two of the strong earthquakes in Iranian history. First was hit by Mw （moment magnitude scale） = 6.4 Richter at local time 16：54 （12：23 GMT （Greenwich Mean Time））, and about 11 min later, an Mw = 6.3 struck 10 km to the west. The spatial-temporal clustering of micro earthquakes （aftershocks） near Varzeghan, is parameterized by means of a generalized passion model. The region has known faults but numerous smaller or deeply buried faults remain undated, according to the Geological Survey of Iran.

The M_S 4.1 Reservoir-induced Hujiaping Earthquake in the Yangtze Three Gorges Reservoir Region

In this paper,based on the collected data and earthquake field investigation,characteristics of the MS4.1 Hujiaping earthquake of November 22,2008 at Guizhou town in Zigui county,Hubei Province and the geological and hydrogeological conditions and seismicity background of the area are analyzed,and the earthquake disaster is presented. Some scientific issues relating to earthquake precursors and the cause of the earthquake is discussed. The authors consider that the earthquake is a tectonic type reservoir-induced earthquake,occurring along the Xiannvshan fault under the joint action of reservoir water loading and water infiltration,and that there were certain suspected anomalies appearing in the gravity field before the earthquake. The cause of the earthquake may also be related to the effect of the Wenchuan earthquake on the local stress field.

Seismicity of the San Francisco Volcanic Field of Northern Arizona

Seismicity in northern Arizona is concentrated in a northwest-southeast trending belt that stretches from the Utah border south to the edge of the Colorado Plateau. Located within this NASB （Northern Arizona Seismic Belt） is the San Francisco volcanic field, classified by the United States Geological Survey as potentially active. The last volcanic event in the field was located at Sunset Crater and occurred less than 1,000 years ago. Eruption intervals in the volcanic field are of the same order of length of time. Seismic monitoring of the volcanic field area has improved greatly since 1985 with the establishment of new network seismic stations. This has allowed for a lowered threshold of detection of seismic events and improved location capabilities. As an example of the result of this improved ability to locate smaller tremors, two swarms have been identified in the field, the 2009 Halloween swarm near Sunset Crater volcano and the 2011 swarm near Flagstaff, the largest urban community in northern Arizona.