东南沿海地震形势分析

研究１９００年以来东南沿海地震活动序特征，并进行了地震活动分幕，结果表明，１９８６年开始进入了本世纪以来的第Ｖ地震活跃幕，本活跃幕将延至２０００年左右，期间有发生６级左右地震的危险，最大可能的发震区是闽粤交界及其沿海地区。     

Seismic sea-waves in the Marmara Sea region during the last 20 centuries

An examination of historical sources confirms thatrelatively little can be found about seismic sea-waves in the Marmara Searegion. We find that during the last 20 centuries there have been 16earthquakes which seem to be associated with seismic sea-waves, six ofwhich were damaging. Most of these events were reported from the northcentral and north-east coast of the Sea of Marmara and from the Gulf ofIzmit, from where there is some evidence that the source mechanism ofsome of them was coastal mass failures and sliding of submarine sediments.Another 16 sea-waves reported in literature are found to be spuriousevents.     

Tsunami hazard in the shorelines of Khark island (Persian Gulf), Iran

Iran is located in one of the seismically active regions of the world. Due to the high probability of earthquakes throughout the country and the potential for tsunami inundation along the coasts and offshore, comprehensive studies on the interaction of these natural phenomena are necessary. In this study, the most conservative scenarios are determined for possible earthquakes within the Khark zone (Persian Gulf) based on experimental relations between the fault length, magnitude and displacement, which are parameters for determining tsunamigenic sources. Subsequently, the maximum height of tsunami waves are calculated based on the specifications of the seismic source and its distance from the shore as well as the coastal slope. A zoning map of tsunami hazard is finally presented.     

Population Expousure in the High Seismic Hazard AREA of Low-elevation Coastal Zone in China from 1990 to 2015

中国沿海低地人口稠密、经济发达,是包括地震在内的自然灾害频发地区。由于已有研究成果缺乏对地震灾害暴露和风险的研究,本文利用CoastalDEM、Worldpop人口和中国地震动参数区划等数据,分析1990—2015年中国沿海低地地震高危险性地区人口暴露时空变化特征。研究结果表明,中国沿海低地地震高危险性地区面积为15.1×104 km2,约占全国沿海低地总面积的70.6%;1990—2015年,沿海低地地震高危险性地区暴露人口不断增加,2015年暴露人口达16869万人,与此同时,城市人口快速增长,而农村人口大幅下降。     

东南沿海地震带一组主导强震的准同步活动特征

回顾了1994年台湾海峡南部7．3级地震和1994～1995年北部湾6．1级、6．2级双震的孕育、发生和调整过程,认为这两次强震快速呼应,具有成组和准同步的活动特征,主导了东南沿海地震带第四个活跃幕的中强地震活动总体格局。     

Seismic gaps and source zones of recent large earthquakes in coastal Peru

The earthquakes of central coastal Peru occur principally in two distinct zones of shallow earthquake activity that are inland of and parallel to the axis of the Peru Trench. The interface-thrust (IT) zone includes the great thrust-fault earthquakes of 17 October 1966 and 3 October 1974. The coastal-plate interior (CPI) zone includes the great earthquake of 31 May 1970, and is located about 50 km inland of and 30 km deeper than the interface thrust zone. The occurrence of a large earthquake in one zone may not relieve elastic strain in the adjoining zone, thus complicating the application of the seismic gap concept to central coastal Peru. However, recognition of two seismic zones may facilitate detection of seismicity precursory to a large earthquake in a given zone; removal of probable CPI-zone earthquakes from plots of seismicity prior to the 1974 main shock dramatically emphasizes the high seismic activity near the rupture zone of that earthquake in the five years preceding the main shock. Other conclusions on the seismicity of coastal Peru that affect the application of the seismic gap concept to this region are: (1) Aftershocks of the great earthquakes of 1966, 1970, and 1974 occurred in spatially separated clusters. Some clusters may represent distinct small source regions triggered by the main shock rather than delimiting the total extent of main-shock rupture. The uncertainty in the interpretation of aftershock clusters results in corresponding uncertainties in estimates of stress drop and estimates of the dimensions of the seismic gap that has been filled by a major earthquake. (2) Aftershocks of the great thrust-fault earthquakes of 1966 and 1974 generally did not extend seaward as far as the Peru Trench. (3) None of the three great earthquakes produced significant teleseismic activity in the following month in the source regions of the other two earthquakes. The earthquake hypocenters that form the basis of this study were relocated using station adjustments computed by the method of joint hypocenter determination.     

Source mechanisms of the June 2004 Tabuk earthquake sequence, Eastern Red Sea margin, Kingdom of Saudi Arabia

A sequence of earthquakes took place in June 2004 approximately 60 km southeast of Tabuk, Saudi Arabia. The first felt event (M _W = 3.9) occurred on June 9 and caused minor damage in the epicentral area according to the National Earthquake Information Center and the local reports. Another moderate size event occurred on June 22 (M _W = 5.1) and was followed by a few felt aftershocks without any reported damage. This earthquake sequence caused considerable alarm at Tabuk and highlights the fact that damaging earthquakes can occur in this region away from the major plate boundary in the Red Sea. Being the largest well-recorded event in the area for which the digital and broadband records from Saudi Arabia, Egypt, Israel, Jordan, Turkey, Cyprus, and Kuwait are available, it provides an excellent opportunity to study the tectonic process and present day stress field acting on this area. The digital records from these regional networks were used to relocate the largest three events of this sequence. Focal mechanisms were obtained from full waveform inversion and indicate normal faulting mechanisms with two nodal planes oriented NW–SE in parallel to the faults bounding the Tabuk graben and the Red Sea rift axis. These events originated at shallow focal depths of 4–5 km, possibly contributing to the widely felt ground motions. These events offer a unique opportunity to study the active tectonics of the region as well as inform future studies of seismic hazard in northwestern Saudi Arabia, the Gulf of Aqaba, and eastern Egypt.     

Seismic Sources on the Iberia-African Plate Boundary and their Tectonic Implications

—The plate boundary between Iberia and Africa has been studied using data on seismicity and focal mechanisms. The region has been divided into three areas: A; the Gulf of Cadiz; B, the Betics, Alboran Sea and northern Morocco; and C, Algeria. Seismicity shows a complex behavior, large shallow earthquakes (h < 30 km) occur in areas A and C and moderate shocks in area B; intermediate-depth activity (30 < h < 150 km) is located in area B; the depth earthquakes (h 650 km) are located to the south of Granada. Moment rate, slip velocity and b values have been estimated for shallow shocks, and show similar characteristics for the Gulf of Cadiz and Algeria, and quite different ones for the central region. Focal mechanisms of 80 selected shallow earthquakes (8 m_b 4) show thrust faulting in the Gulf of Cadiz and Algeria with horizontal NNW-SSE compression, and normal faulting in the Alboran Sea with E-W extension. Focal mechanisms of 26 intermediate-depth earthquakes in the Alboran Sea display vertical motions, with a predominant plane trending E-W. Solutions for very deep shocks correspond to vertical dip-slip along N-S trends. Frohlich diagrams and seismic moment tensors show different behavior in the Gulf of Cadiz, Betic-Alboran Sea and northern Morocco, and northern Algeria for shallow events. The stress pattern of intermediate-depth and very deep earthquakes has different directions: vertical extension in the NW-SE direction for intermediate depth earthquakes, and tension and pressure axes dipping about 45 ° for very deep earthquakes. Regional stress pattern may result from the collision between the African plate and Iberia, with extension and subduction of lithospheric material in the Alboran Sea at intermediate depth. The very deep seismicity may be correlated with older subduction processes.     

闽粤海外历史地震与台湾海峡现今强震活动图像

闽粤两省强烈地震多发生在沿海地区,且福建南日岛至广东南澳一线的泉州－汕头地震带地震活动尤为突出。历史上东南沿海地震带曾发生过４次７级以上大地震,而其中３次都发生在泉－汕段海域,继华南地区本世纪著名的１９１８年广东南澳７．３级地震后,１９９４年９月１６日台湾海峡南部又发生７．３级强震,这在经济发达,人口稠密的闽粤沿海地区引起了极大关注。本文通过历史强震活动资料,分析闽粤沿海与台湾海峡强震在时间进程,     

东南沿海活动地块的初步划分

东南沿海地区无论过去还是现在都是华南中强地震多发区，西文度菌 从地质、地球物理和地球化学相结合的角度，并根据地震学、海洋地质学及深部构造物理资料，对东南沿海活动地块作一个初步划分，并对其地震活动性作了初步分析，得出了地块内部比较统一的地震活动图像。     

极值理论在福建沿海地区地震预测中的研究与应用

利用陈培善等人对极值理论修改后的极值分布函数模型对1971年1月-2012年9月福建沿海地区的地震资料进行统计分析,单位时间内最小与最大地震的确定分别考虑相关区域内台网的监控能力以及删除余震后的实际情况.根据修正后的极值理论统计计算出该地区地震的复发周期及截至2015年12月可能发生的相应地震的次数与发震概率,并对有关结果进行映震能力分析,为今后福建沿海地区地震趋势分析提供可遵循的理论依据.     

内蒙古地区非天然地震的特征与识别

基于2014年以来内蒙古测震台网观测报告,对所记录的非天然地震事件进行统计分析。提出了区分天然地震与非天然地震的一般方法。从地震事件的三要素、波形、频谱等方面对比分析内蒙古地区非天然地震与天然地震间的差异发现,内蒙古地区非天然地震具有发震时刻与发震位置较固定与集中、震级M_L<3.5、面波较发育、能量衰减较快、优势频率主要集中在1—6 Hz等特征。并通过对比内蒙古不同地区典型震例,进一步总结出内蒙古地区非天然地震的地方性特征。研究结果有利于提高内蒙古地区非天然地震的识别能力,可为今后开展该区非天然地震自动识别研究提供基础资料。     

Distribution of petroleum hydrocarbons and organochlorinated contaminants in marine biota and coastal sediments from the ROPME Sea Area during 2005

The composition and spatial distribution of various petroleum hydrocarbons (PHs), comprising both aliphatic and polycyclic aromatic hydrocarbons (PAHs), and selected chlorinated pesticides and PCBs were measured in biota and coastal sediments from seven countries in the Persian Gulf and the Gulf of Oman (Bahrain, Iran, Kuwait, Oman, Qatar, Saudi Arabia and the United Arab Emirates). Evidence of extensive marine contamination with respect to organochlorinated compounds and PHs was not observed. Only one site, namely the BAPCO oil refinery in Bahrain, was considered to be chronically contaminated. Comparison of the results from this survey for Σ DDTs and Σ PCBs in rock oysters from the Gulf of Oman with similar measurements made at the same locations over the past two decades indicates a temporal trend of overall decreasing Σ PCB concentrations in oysters, whereas Σ DDTs levels have little changed during that period.     

东北深震与中国大陆主要构造带地震活动的相关性统计分析

统计分析了中国大陆１９００年以来所有发生在东北的５级以上的学震及其与中国大陆２６个地震带６级以上（其中东部为５级以上）地震活动的相关性。结果表明７级以上深震有可能引发中国大陆地震活动进入应变能大释放阶段。其中与东北深震统计相关最高的地震带是：金沙江地震带、南天山地震带澜沧江－眉公河地震带以及巴颜喀拉山地震带;在中国东商地区相关性相对较高的地区是：郯城－营口地震带、长江下游－南黄海地震带以臁东南沿海     

粤闽交界及其近海地区地震活动分析

结合东南沿海地区的地质构造背景、地震活动特点,研究粤闽交界及其近海地区(N 22.80°~24.00°、E116.50°~118.00°)地震活动特征,结果表明此区域:1具备中强地震活动的构造背景;2现代小地震呈北东方向密集成带分布在南澎列岛附近,与北东向滨海断裂的方向一致;3 6级以上地震序列类型多属主余型;4 1971年有小震记录以来,一直存在背景性的ML2级左右地震活动;ML4级以上地震活动成丛分布特征明显;中等地震(ML4~5级)的发生与本区小震活动增强之间无明显关联;当出现年平均b值低于平均值、且较上一年b值下降幅度≥0.5时,可能预示本区进入ML4级地震活跃时段,东南沿海地震带在未来1~2年内可能有中强或以上地震发生;ML4.5级以上地震前,应变能释放曲线存在加速变化。     

用双差定位结果分析华北地区的地震活动

华北地区北部是阴山—燕山隆起区、 华北平原和太行山隆起的交界处, 区域内地震活跃, 北部有张家口—渤海地震活动带(张渤带), 西邻山西地震活动带。 本研究采用双差定位法对华北地区2006—2009年发生的地震进行重新定位, 结果显示, 近年来华北地区的地震主要集中在北部的张渤带上, 总体呈WNW向分布。 震源深度主要集中在0~20 km的中上地壳, 占地震总数的96.3%, 有大约57.5%的地震分布在10 km以上的地壳内。 张渤带东部的唐山地区是该地震带上地震最密集的地区, 地震分布与区域内的断层有密切关系。 华北平原中南部的邢台地区也是地震相对较密集的区域, 定位结果显示, 邢台地区的新河断裂可能深达Moho面, 在该断裂的下方可能存在速度异常体, 把邢台地区西南部的地震活动从空间上隔离成上下两部分。 沿新河断裂的地震分布出现异常, 在深度10 km处, 地震分布由北东向西南逐渐与上部的地震分离, 震源深度逐渐加深, 最深可达30 km左右。     

地震海啸在东海大陆架上传播过程的数值模拟研究

在东海潜在震源区冲绳海槽假定了五个震源点,根据Steven地震海啸地震参数经验值作为初始条件,分别考虑6.5、7.0、7.5、8.0、8.5、9.0级地震条件下的30个震例,采用数值模拟的方法,对海啸在东海传播过程进行情境分析,特别是对上海沿岸地区可能会遭受的海啸灾害做了较为精细的研究.结果发现:小于8.0级的震例对上海地区几乎不会造成影响;8.0级震例只有最北端震源点震例会对上海地区有明显影响;8.5级以及9.0级震级基本上均会对上海沿岸地区造成较大的影响.特别是冲绳海槽北段9.0级震例可能会对上海沿岸局部地区造成危害,最大波高可达3.9m.     

Seismicity and Seismic Hazard in Alexandria (Egypt) and its Surroundings

— Alexandria City has suffered great damage due to earthquakes from near and distant sources, both in historical and recent times. Sometimes the source of such damages is not well known. Seismogenic zones such as the Red Sea, Gulf of Aqaba-Dead Sea Hellenic Arc, Suez-Cairo-Alexandria, Eastern-Mediterranean-Cairo-Faiyoum and the Egyptian costal area are located in the vicinity of this city. The Egyptian coastal zone has the lowest seismicity, and therefore, its tectonic setting is not well known. The 1998 Egyptian costal zone earthquake is a moderate complex source. It is composed of two subevents separated by 4 sec. The first subevent initiated at a depth of 28 km and caused a rupture of strike (347°), dip (29°) and slip (125°). The second subevent occurred at a shallower depth (24 km) and has a relatively different focal parameter (strike 334°, dip 60° and slip 60°). The available focal mechanisms strongly support the manifestation of a complex stress regime from the Hellenic Arc into the Alexandria offshore area. In the present study a numerical modeling technique is applied to estimate quantitative seismic hazard in Alexandria. In terms of seismic hazard, both local and remote earthquakes have a tremendous affect on this city. A local earthquake with magnitude M_s = 6.7 at the offshore area gives peak ground acceleration up to 300 cm/sec². The total duration of shaking expected from such an earthquake is about three seconds. The Fourier amplitude spectra of the ground acceleration reveals that the maximum energy is carried by the low frequency (1–3 Hz), part of the seismic waves. The largest response spectra at Alexandria city is within this frequency band. The computed ground accelerations due to strong earthquakes in the Hellenic Arc, Red Sea and Gulf of Aqaba are very small (less than 10 cm/sec²) although with long duration (up to 3 minutes).     

福建近岸海域滨海断裂的应力分析

福建东南沿海地区曾发生多次强震。本文利用该区1604～1989年的47次地震的震源机制资料,采用力轴张量计算法推算了该区应力主轴方向,结果与其他文献给出的主压应力方向相符,即北西西-南东东向。在此基础上,得到最大剪切应力平面的走向和倾角。讨论了最大剪切应力平面与福建沿海近岸海域中存在的滨海断裂（牛山岛-兄弟屿断裂）的位置关系。从应力分析的角度初步探讨了滨海断裂带上地震活动由北向南增强的原因。     

Corresponding Relation Between the Space-time Evolution of Seismic Apparent Strain and the Region of Strong Earthquakes in Yunnan

On the basis of our predecessors' research,we study the distribution and the space-time evolution characteristics of the seismic apparent strain field in Yunnan since the 1970's using the seismic data of Yunnan and its surrounding areas.The result shows that there is a rather strong corresponding relationship between the anomaly region of seismic apparent strain and strong earthquakes.In the nine earthquakes studied,anomaly areas of seismic apparent strain had appeared before eight earthquakes,including five occurring in the anomaly region and three on the edge.Finally,the investigative result is demonstrated primarily.