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1.
S. A. Kovachev I. P. Kuzin L. I. Lobkovskii 《Izvestiya Physics of the Solid Earth》2009,45(9):777-793
The results of detailed seismological observations with bottom seismographs in the Central Kurile segment in August-September,
2006 are discussed. The system of six bottom seismographs was placed on the island slope of the Kurile deep-sea trench southeast
of Urup Island and southwest of the Bussol Strait. Over 230 earthquakes with M
LH = 0.5–5.5 were registered in the area with a radius of 150 km around the center of the observation system at depths up to
300 km during 16 days. Records of 80 earthquakes with hypocenters in the earth crust (h = 0–30 km) beneath the island slope of the Kurile deep-sea trench were first obtained by bottom seismographs. These data
are inconsistent with previous concepts of aseismicity of this zone. The discovery of the unique morphological structure of
the Benioff zone beneath the central Kurile Arc represents the most important result of detailed seismological observations.
The zone consists of an inner seismoactive subzone, which is located beneath the island slope of the arc at depths of 15–210
km, being characterized by an angle of incline of 50° under the latter and crosses the ocean bottom approximately 80 km away
from the trench axis, and outer low-activity subzone. The latter is traceable beyond the trench almost parallel to the inner
zone beginning from a depth of 50 km below the sea bottom up to a depth of approximately 300 km. Due to the slightly lower
incline (∼45°) of the outer subzone, both subzones gradually converge downward. The integral thickness of the Benioff zone
varies from 150 km in its upper part to 125 km at depths of 210–260 km. The medium sandwiched between these subzones is practically
aseismic. The reality of this defined structure is confirmed by the distribution of aftershocks of the earthquake that occurred
on November 15, 2006 (M = 8.3). These seismic events served as foreshocks for the subsequent strong earthquake of January 13, 2007 (M = 8.1) with the hypocenter located beyond the trench under the ocean bottom. Such a structure of this zone within the central
Kurile Arc segment is unique, having no analogues either in the flanks of the Kurile-Kamchatka Arc or other arcs. The results
of detailed seismological observations obtained two months before the first of the catastrophic Central Kurile earthquakes
appeared to be typical for the period of foreshocks (the lower seismic activity of the Simushir block, which hosted the hypocenter
of the earthquake that occurred on November 15, 2006, particularly at depths of 0–50 km, the gentler incline of the recurrence
plot, and other features). 相似文献
2.
M. Rizwan M. Ilyas A. Masood I. Towhata 《Soil Dynamics and Earthquake Engineering》2008,28(4):328-332
Pakistan has a long history of seismological activity. The devastation caused by Kashmir earthquake has been administered all over the world. In Pakistan first seismological network, consisting of analog accelerograms and seismographs, was setup in early 1969 at Tarbela, where the largest water reservoir of the country is located. An approach to convert analog ground motion records into digital form is explained using a simple technique. The digitized data was compared with the original analog record and found in good agreement. The data has been used to plot response spectra. The digitized data will be available for seismic response analysis of structures and seismic risk analysis of the region. 相似文献
3.
本文应用地震拓扑预测方法,对华北地区进行了地震长期趋势估计。通过实例计算证明,其拓扑预测模型精度较高,可以预测该区未来强震的危险性。 相似文献
4.
地震的孕育和发生除了与区域背景构造应力的增长变动有关,也是震源区应力增长及破裂发展的结果.因此地震观测资料必然携带有震源区应力应变增长及破裂发展的信息.随着数字地震观测台网的普及和数字地震仪性能的提高,用地震观测资料进行震源区应力变化和破裂过程的研究已成为国际地震学界的研究热点.本文综述了岩石静态应力状态的变化对地震波传播与衰减的影响,及其对地震孕育和激发的作用;主要介绍了利用地震观测资料预测震源区应力变化的主要研究方法和目前的进展;讨论了该研究领域未来的发展前景,作为进一步研究的基础. 相似文献
5.
震源机制解,即对地震矩张量的推断,对于地震研究具有至关重要的意义.应变地震观测是张量观测,与摆式地震仪的位移矢量观测不同,可以为地震研究提供新的数据源.本文讨论用应变地震观测求解震源矩张量的基本原理.在距离震源足够远的地方,地震波可以看成平面波,其性质决定于震源矩张量.假设平面地震波的应变张量可以由震源矩张量通过坐标变换计算得到,就可以通过观测应变地震波求解震源机制.这个假设至少对于双力偶震源机制是成立的.由此可以证明,在理想的无限介质中,只要有两个以上不同地点的应变地震波观测,就可以解出震源矩张量.这为解决震源机制问题提供了新的方法.目前的地震矩张量求解方法需要两方面的条件:或者需要很多观测点(例如体波反演),或者需要长周期地震波资料(例如面波反演).这些方法只适用于分析比较大的地震.对于小震,因为通常其震中周围不会有足够多的摆式地震仪观测点观测到其地震波,而地震波周期又短,难以利用传统方法给出可靠的震源机制解,所以只需少数观测点就能求解震源矩张量的新方法特别有意义.用应变地震观测求解震源机制,可以给出更为精确的结果. 相似文献
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7.
Summary Two electromagnetic seismographs HSJ-I, which are coupled with short-period galvanometers, record the velocity of the ground motion in the range of periods from 0.3 to 20 s in the seismological station Moxa. In this way the magnitude of an earthquake can be calculated without respect to the period of the ground motion. The results of such a determination of magnitudes are compared with those reached in the usual manner from short and long-period seismographs recording the ground displacement.Publication No. 45 of the Institut für Geodynamik, 69 Jena (DDR), Burgweg 11, der Deutschen Akademie der Wissenschaften zu Berlin, Forschungsgemeinschaft. Presented at the IUGG-Assembly, Zurich 1967. 相似文献
8.
Specially designed arrays of strong-motion seismographs near to the earthquake source are required for seismological and engineering studies of the generation and near-field properties of seismic waves. The first such large digital array, called SMART 1 (with radius 2 km and 37 accelerometers), to record substantial ground motion (up to 0·24g horizontal acceleration) became operational in late 1980 in a highly seismic region of Taiwan. During the first 6 months of operation, SMART 1 recorded nine earthquakes with magnitudes ranging from ML 3·8 to 6·9. Three were located directly below the array at focal depths of 59 to 76 km. The remaining six had shallow depths and epicentral distances from 7 to 193 km. Digital records from 27 three-component accelerographs were obtained from a magnitude 6·9 (ML) local earthquake on 29 January 1981. Representative measurements are described of seismic wave coherency and power spectrum as a function of wave number, frequency, azimuth of propagation and wave type. Acceleration waveforms varied significantly across the array for each event. On average, peak acceleration of horizontal components was about three times that of the vertical component. Relative spectral changes from earthquake to earthquake were large. 相似文献
9.
本文根据最小相位系统判据,对目前我国地震台站普遍使用的几种类型地震仪做了分析指出,这些仪器都是最小相位系统;最小相位系统的相频特性可由其幅频特性计算出来.作者按照地震台站观测规范规定,标定了 DD-1型、DK-1型和基式地震仪的幅频特性.然后,用希尔伯特(Hilbert)变换由实测幅频特性计算了它们的相频特性.并把计算结果与用相位特性测试仪器实测的结果做了比较:对于 DD-1型地震仪,在从0.0125秒到12.5秒的周期范围内,最大误差小于5;对于 DK-1地震仪,在从0.05秒到100秒的周期内,最大误差小于5;对于基式地震仪,在从0.01秒到100秒的周期范围内,最大误差小于1.5.这种方法可以解决台站仪器相频特性的标定问题.标定精度比快速傅里叶变换(FFT)方法和用近似解析表达式计算方法要高.应用这种方法的关键是能对被测系统幅频特性曲线高频段和低频段的斜率做出正确的判断.这种方法的误差取决于幅频特性曲线的标定精度.用插值方法计算,计算的尾差和截断误差可以不必考虑. 相似文献
10.
Ma Wentao~ Xu Changpeng~ Yuan Jingli~ Li Hai’ou~ Xu Xiwei~ Zhang Xindong~ Zhang Lanfeng~ 《中国地震研究》2011,25(3):273-285
In accordance with the requirements of the National Key Technology R&D Program of the 11th "Five-year Plan",a densified seismic network consisting of 26 seismic stations was established at the Three Gorges Reservoir area in the section of Hubei Province in March 2009(21 short-period seismographs,5 broadband digital seismographs).From March to December,2009,a total of 2,995 ML-0.8~2.9 earthquakes were detected during the trial impounding of the Three Gorges Reservoir(water level rose from 145 m to 172.8m).Using the double difference earthquake location algorithm,2,837 earthquakes were precisely re-located.The results show that the pattern of small local earthquake swarms in the Three Gorges Reservoir area took on a linear distribution or mass-like cluster distribution,the mass-like clusters of events were generally within a distance of 5 km from waterfront,and the linear distribution of the earthquakes could be extended to a distance of 16 km away from the waterfront.In the Hubei section of the Three Gorges Reservoir,earthquakes were mainly concentrated in the northern end of the Xiannvshan and Jiuwanxi faults near the Xiangxihe River,and along the banks of the Yangtze River at the west of Xietan township and the Shenlongxi area on the northern bank in the Badong region,with focal depths less than 10km,and 4km in average.Earthquake frequency in the reservoir region had a positive correlation with reservoir water level fluctuations,indicating that the seismicity belongs to reservoir induced earthquakes.Along the Shenlong River in the reservoir area,earthquakes showed three linear distributions in the northern Badong county,and distributed according to Karst distribution.There are underground rivers in the carbonate strata.When the reservoir was impounded,water permeated into the underground rivers,thus inducing earthquakes.Earthquakes in the areas on the cross-river segment of Xiannvshan fault,the Jiuwanxi fault and at the areas west of Xietan,Shazhen and Xizhen,may be related to the softening of discontinuities,such as the Nukou fault,the Xiannvshan fault,or the bedding joints,which would lead to failure of rock masses,thus,inducing earthquakes.However,convincing conclusions about the triggering mechanism still need further study.Additionally,near the areas south of Wenhua and Yanglin of Zigui county and at Rangkou town east of Badong county,mining-induced earthquakes occurred at the mines nearby,and on the shores of the reservoir are some collapse earthquakes. 相似文献
11.
本文主要讨论观测仪器的质量问题, 着重讨论影响初动的有关仪器部件和它们的参数.提出用升起时间ts作为评价仪器记录初至波质量好坏的特性参数.给出升起时间ts和仪器频带之间的关系.对我国地震台站上常用地震仪器的升起时间作了比较. 相似文献
12.
以多分量地震观测为基础,联合纵波和转换横波数据能更有效地估计地下介质的弹性和物性参数,提升地质构造成像与油气储层描述的精度.在海底多分量地震数据处理过程中,观测记录的上-下行波分解和P/S波分离可压制水层鸣震以及P与S波之间的串扰,对偏移成像和纵横波速度建模至关重要.但受海底环境、仪器与观测因素共同影响,许多海底多分量地震资料都无法基于现有的海底波场分离方法与流程取得合理的结果.本文以海底声波场与弹性波场分离基本原理为基础,通过对方法流程的修正,摆脱常规流程对中小偏移距直达波信号的依赖性.借助模拟数据实验讨论了波场分离对海底介质参数、噪声的敏感性.结合东海YQ探区海底多分量地震资料上-下行P/S波分离及其叠前深度偏移处理,验证了本文方法流程的可行性. 相似文献
13.
本文根据AKi单次逆向散射的尾波理论,应用Herrmann等人推广了的尾波理论模式,并假设Q与频率相关,计算了58-1,63-B和DSL-1三种短周期地震仪的尾波优势频率、尾波形状和尾波斜率作为t*函数的理论曲线,并利用库区四个台58-1仪器记录的新丰江库区的地震资料,用S-t*和C-t*两种方法,估算了新丰江水库区频率约为1.0Hz短周期波的地壳Q0值,得到Q0值在170——300之间,平均为23038;频率相关系数为0.0——0.2。Q0的平面分布表明,近坝峡谷区具有最低的Q0值。与其他地区对比后认为,库区属于地质构造相对稳定的地区。 文中还对尾波Q值的估测方法等若干问题进行了讨论。 相似文献
14.
R. E. Tatevossian A. Ugalde Zh. Ya. Aptekman A. E. Petrosyan 《Izvestiya Physics of the Solid Earth》2006,42(2):124-131
The possibility to obtain a more complete and unbiased long-term history of seismic shakings over large territories than is explicitly reported from inhabited localities is discussed in the paper. An approach proposed for this purpose consists in complementing the spatial distribution of the macroseismic effect of earthquakes by calculated intensities at localities where information on felt shakings is absent. The calculated intensity is obtained on the basis of data on the epicentral intensity and location of epicenters provided by earthquake catalogs. This approach is applied to the analysis of the history of seismic shaking in Spain. The calculated intensities are shown to be comparable in accuracy with the ordinary practice of intensity determinations at national seismological centers. 相似文献
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16.
针对烟记录地震仪存在的问题，采取仅改动其放大器、电源与记录部分，利用现有拾震器和大滚筒记录器，投入少量资金，即可改造成适合台站使用的新型ＤＹＪ－１型短周期墨水记录地震仪。 相似文献
17.
Gholamreza Abdollahzadeh Mohammad Sazjini Mohsen Shahaky Fatemeh Zahedi Tajrishi Leila Khanmohammadi 《Journal of Seismology》2014,18(3):357-369
Located on the Alpine-Himalayan earthquake belt, Iran is one of the seismically active regions of the world. Northern Iran, south of Caspian Basin, a hazardous subduction zone, is a densely populated and developing area of the country. Historical and instrumental documented seismicity indicates the occurrence of severe earthquakes leading to many deaths and large losses in the region. With growth of seismological and tectonic data, updated seismic hazard assessment is a worthwhile issue in emergency management programs and long-term developing plans in urban and rural areas of this region. In the present study, being armed with up-to-date information required for seismic hazard assessment including geological data and active tectonic setting for thorough investigation of the active and potential seismogenic sources, and historical and instrumental events for compiling the earthquake catalogue, probabilistic seismic hazard assessment is carried out for the region using three recent ground motion prediction equations. The logic tree method is utilized to capture epistemic uncertainty of the seismic hazard assessment in delineation of the seismic sources and selection of attenuation relations. The results are compared to a recent practice in code-prescribed seismic hazard of the region and are discussed in detail to explore their variation in each branch of logic tree approach. Also, seismic hazard maps of peak ground acceleration in rock site for 475- and 2,475-year return periods are provided for the region. 相似文献
18.
Results of seismological observations in the western Kaliningrad region and in the Baltic Sea water area 总被引：1，自引：1，他引：0
S. A. Kovachev 《Izvestiya Physics of the Solid Earth》2008,44(9):706-716
In 2006–2007, researchers of the IO RAS conducted seismological observations in the Baltic Sea and western Kaliningrad region with the use of ocean-bottom and land-based autonomous seismic stations. According to maps of general seismic zoning of the territory of Russia, the Kaliningrad region is aseismic. However, a series of seismic phenomena with magnitudes of about 5 and sources located near the Bay of Gdansk coast occurred here in September 2004. The total duration of the IO RAS seismological observations in five areas of the region under investigation was more than 200 days. The analysis of seismic records of the IO RAS network located sources of two local weak earthquakes with magnitudes M L = 3.4–3.5, which indicates that the seismic process in the western part of the Kaliningrad region continues and the region is far from being seismically stable. 相似文献
19.
Koichiro Obana Shuichi Kodaira Yoshiyuki Kaneda 《Earth and Planetary Science Letters》2004,222(2):561-572
Along the Nankai trough, southwestern Japan, the Philippine Sea plate (PSP) is subducting beneath the Eurasian plate, and large interplate earthquakes have occurred repeatedly with a recurrence interval of about 100-200 years. The most recent large thrust event in the eastern Nankai trough off Kii Peninsula was the 1944 Tonankai earthquake. In this region, current seismicity is very low and hypocenters are not determined accurately by the land seismic network. We conducted microseismicity observations around the rupture area of the 1944 Tonankai earthquake using ocean bottom seismographs (OBSs). Hypocenters were determined using a 2-D seismic velocity structure model based on an airgun-OBS seismic survey. Results obtained show that the seismicity was relatively active near the trough axis. These earthquakes may relate to deformation of the subducting Philippine Sea plate. On the other hand, microseismicity in the rupture area of the 1944 Tonankai earthquake was very low. This low-level seismic activity in the co-seismic rupture area of the 1944 Tonankai earthquake likely relates to a single large asperity off Kii Peninsula. 相似文献
20.
SEISMO-GEOLOGICAL SIGNATURES FOR IDENTIFYING M≥7.0 EARTHQUAKE RISK AREAS AND THEIR PREMILIMARY APPLICATION IN MAINLAND CHINA 
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下载免费PDF全文 High-magnitude earthquake refers to an earthquake that can produce obvious surface ruptures along its seismogenic fault and its magnitude M is at least equal to 7.0. Prediction and identification of locations, where the high-magnitude earthquakes will occur in potential, is one of the scientific goals of the studies on long-term faulting behavior of active faults and paleo-earthquakes, and is also the key problem of earthquake prediction and forecast. The study of the geological and seismological signatures for identifying M≥7.0 earthquake risk areas and their application is an important part of seismic prediction researches. It can not only promote the development of earthquake science, especially the progress of earthquake monitoring and forecasting, but also be positive for earthquake disaster prevention and effective mitigation of possible earthquake disaster losses. It is also one of the earthquake science problems which the governments, societies and the scientific communities are very concerned about and need to be addressed.
Large or great earthquakes, such as the 2008 Wenchuan earthquake(M8.0), the 2010 Yushu earthquake(M7.1), the 2013 Lushan earthquake(M7.0)and the 2015 Gorkha earthquake(MW7.8), have unceasingly struck the Qinghai-Tibet Plateau and its surrounding areas, which have been attracting attention of a large number of geoscientists both at home and abroad. Owing to good coverage of the seismic networks and GPS sations, a lot of high-quality publications in seismicity, crustal velocity structure, faulting beihavior have been pressed, which gives us a good chance to summarize some common features of these earthquakes. In this paper, seismogenic structural model of these earthquakes, faulting behavior of seismogenic faults, crustal mechanical property, recent straining environment and pre-earthquake seismicity are first analyzed, and then, five kinds of common features for the sismogenic faults where those earthquakes occurred. Those five kinds of commom features are, in fact, the geological and seismological signatures for identifying M≥7.0 earthquake risk areas. The reliability of the obtained sigatures is also discussed in brief. At last, based on the results of 1:50000 active fault mapping, and published seismic tomography and fault-locking studies, an experimental identification of the risk areas for the future large/great earthquakes in the North China and the Qinghai-Tibet Plateau is conducted to test the scientificity and applicability of these obtained sigantures. 相似文献