共查询到20条相似文献，搜索用时 22 毫秒
1.
2.
Chunyan Zhang Sidao Ni Key Lab of Intelligent Computing Signal Processing of Ministry of Education School of Mathematics Anhui University Hefei China Key Laboratory of Dynamic Geodesy 《地震学报(英文版)》2011,(1):127-132
We analyzed the seismic waveforms from the December 26,2004 Sumatra-Andaman earthquake recorded at broadband seismic stations in western Europe.Previous studies involving of the beam-forming technique and high frequency analysis suggest that the earthquake ruptured with a duration of around 500 s.This very long duration makes P wave overlap with later arrivals such as PP wave,which follows P in about 200 s.Since P waves are crucial for modeling earthquake processes,we propose an iterative method to separate... 相似文献
3.
Study on rupture zone of the M=8.1 Kunlun Mountain earthquake using fault-zone trapped waves 总被引：1，自引：0，他引：1
Introduction The study on deep crustal faults has been one of the most vigorous subjects in seismology. In the past, 3-D deep seismic sounding and 3-D seismic tomography were usually used for this pur-pose. But it is difficult to obtain the fine structures of the faults in deep crust by these methods. Recently, seismologists in the world pay more attention to the fault zone trapped waves. Since the fault-zone trapped waves arise from coherent multiple reflections at two boundaries of the fau… 相似文献
4.
井水位长周期事件记录及其机理的讨论 总被引：13，自引：1，他引：12
选择了几口具有代表性的观测井, 并对这些井孔在强震前记录到长周期波现象的特征进行了分析。从理论上对地震前的长周期事件给出了较为合理的解释, 认为地震前一些敏感井水位长周期事件可能反映了断层蠕动、静地震与慢地震、断裂的预扩展和地震成核等。井— 含水层系统像一个长周期地震仪, 它为记录到有价值的前兆低频波提供了最佳的频率响应范围。 相似文献
5.
利用横跨地表破裂带的小点距的地震测线, 对2001年11月14日昆仑山口西8.1级地震进行了断层围陷波的观测实验. 经过数字滤波和频谱分析等技术, 由地震记录图中分离出了断层围陷波. 资料处理结果表明: ① 无论是人工地震震源还是天然地震震源, 只要位于断层带内或紧靠断层带, 均能激发断层围陷波; ② 断层围陷波的能量主要集中于断层带内, 其振幅随测点与断层带距离的增加而急剧衰减; ③ 断层围陷波的优势频率与断层的宽度及断层带内介质的速度有关, 断层带越宽, 或断层带内部介质速度越低, 则观测到的断层围陷波的优势频率越低; ④ 断层围陷波存在着频散现象; ⑤ 根据昆仑山口西地震测线断层围陷波的观测结果, 可推断该处破裂面宽度为300 m左右, 远远大于地表破裂带的宽度. 相似文献
6.
董晨阳 《地震地磁观测与研究》2021,42(4):133-138
选取镇江市地震台RZB型分量钻孔应变仪2014年5月至2018年3月记录的全球142次地震,探讨该应变仪地震记录能力,分析震级、震中距与最大振幅之间的关系,以及地震波传播方向与四分量中振幅最大分量方位的关系。结果发现：该应变仪可记录研究时段全球发生的所有8级以上地震,理论上震级越大,记录的地震震中距越大;震级相同,震中距越大,应变仪记录的地震波最大振幅越小,拟合曲线较为符合幂函数关系;震中距相近,震级越大,应变仪记录的地震波最大振幅也越大,拟合曲线较为符合幂函数关系。偶有数据点偏离拟合曲线较远,是因为：①地震震源较深;②应变量的最大值或最小值未被记录到,量取值非实际最大和最小振幅;③有时地震波形周期难以分辨。多数地震最大振幅所在分量方向与地震传播方向基本相同。 相似文献
7.
Rupture imaging of the 25 April 2015 MW7.9 Nepal earthquake from back-projection of teleseismic P waves 
下载免费PDF全文
下载免费PDF全文 The MW7.9 Nepal earthquake of 25 April 2015 had over 8, 500 fatalities and was the most destructive earthquake in Nepal since the Bihar-Nepal earthquake in 1934. In this study, we imaged the rupture process of this Nepal event by back-projecting the teleseismic P-wave energy recorded at the three regional networks in Alaska, Australia and Europe. The back-projection images of the three subarrays revealed that the Nepal earthquake propagated along the strike in a southeast direction over a distance of ~ 160–170 km with the duration of ~ 50–55 s. The rupture process was found to be a simple, unilateral event with a near constant velocity of 3.3 km/s. The beam power was mainly distributed in the geographic region just north of Kathmandu and the peak intensity for the source time function curve occurred at about 30 s. The earthquake was destructive due to its occurrence at shallow depth (~ 12–15 km) and the fact that the capital lies in a basin of soft sediment. Additionally, the resonance effect for the longer period waves that occurred in the Kathmandu valley led to destructive aggravation, impacting mainly the taller buildings. 相似文献
8.
本文根据地震和地震构造等资料，研究华北地区公元1300年以来MS≥6.5级地震的发震断裂的基本参数.利用1966年以来隆尧、海城、渤海和唐山等有仪器记录的地震的相关参数进行回归分析得出了地震烈度Ⅷ度区长轴长度与余震区长轴长度的回归关系式及震级与震源体破裂长度的回归关系式.用余震区长轴长度代替震源体的破裂长度，从而给出各次地震的震源断层破裂长度.利用地震测深的地壳结构构造剖面、地震序列的震源分布、壳内低速层和地壳上部的构造、盆地构造与居里面分布和已知地震震源分布等资料推断了震源破裂的上下界.基于一定的合理假定推导出了断层滑动角的估计方法，并应用于本研究区，得出了各次事件的断层滑动角. 相似文献
9.
Satoshi Fujita Keisuke Minagawa Go Tanaka Haruo Shimosaka 《Soil Dynamics and Earthquake Engineering》2011
Recently strong seismic waves or long period seismic waves have been observed in various earthquakes that occurred in Japan. As a result improvements of existing seismic isolation systems are deemed necessary. The present study proposed an intelligent seismic isolation system encompassing air bearings and earthquake early warning (EEW) system. Such system exhibits adequate isolation performance. The air bearings are isolation device that may render infinite the superstructure natural period by floating them, and the EEW is applied for a trigger of isolation. This paper illustrates the proposed system and discusses the experimental results of a test carried out with the system. Laboratory tests carried out in the present research demonstrate the effectiveness of the proposed base isolated systems and prove its efficacy in mitigating the effects of three-dimensional seismic waves. For example, the system suppressed the horizontal response acceleration of an isolation target to 38% of input acceleration. 相似文献
10.
张北地震前小震活动和余震序列精确定位及主震破裂方向的讨论 总被引：3，自引：0，他引：3
1970年至1998年1月10日张北地震前,沿NWW向发生2级以上地震24次,其分布相对集中,呈条带状。对华北台网所记上述地震的到时数据全部重新查图核对,并补充了内蒙古台网5个台的数据以改善用于定位的台站分布,并采用主地震定位法重新定位,除一个地震外,其余地震更加集中,形成一小震条带。1998年2月中国地震局地球物理勘探中心在张北震区架设10台短周期数字化地震仪,记录了大量微震。作者采用P波和S波到时差重新进行了震源定位,得到184次微震的定位结果,连同1998年1～2月张北震区3级以上地震事件定位结果一起勾画出6．2级地震的震源破裂带。由张北地震震中向SEE向延伸存在由强震构成的张家口渤海地震带。根据精确定位结果,结合修订后主震的震源机制、宏观烈度分布和层析成像资料,讨论了张北地震和小尺度地震带(震源破裂带)、震前的中等尺度小震条带以及大尺度的张家口-渤海强震带的关系。 相似文献
11.
强地震的孕育过程也是孕震介质的形成过程,在强震前震源附近小地震的地震波运动学,动力学特征的变化过程,则反映了孕震介质的变化过程,为研究地震的孕育,发展和发生的过程,采用单台地震波振幅比,尾波持续时间比,尾波衰减系数这３项地震波参数作为地震学短期前兆指标,分析其震兆特征,从而达到监测孕震介质变化的目的,研究结果表明,单台地震波参数能够有效地发现地震的前兆,但地震波参数的前兆图像复杂多变,不具有统一的 相似文献
12.
Yuehua Zeng 《Pure and Applied Geophysics》2006,163(2-3):533-548
One of the many important contributions that Aki has made to seismology pertains to the origin of coda waves (Aki, 1969; Aki
and Chouet, 1975). In this paper, I revisit Aki's original idea of the role of scattered surface waves in the seismic coda.
Based on the radiative transfer theory, I developed a new set of scattered wave energy equations by including scattered surface
waves and body wave to surface wave scattering conversions. The work is an extended study of Zeng et al. (1991), Zeng (1993) and Sato (1994a) on multiple isotropic-scattering, and may shed new insight into the seismic coda wave
interpretation. The scattering equations are solved numerically by first discretizing the model at regular grids and then
solving the linear integral equations iteratively. The results show that scattered wave energy can be well approximated by
body-wave to body wave scattering at earlier arrival times and short distances. At long distances from the source, scattered
surface waves dominate scattered body waves at surface stations. Since surface waves are 2-D propagating waves, their scattered
energies should in theory follow a common decay curve. The observed common decay trends on seismic coda of local earthquake
recordings particular at long lapse times suggest that perhaps later seismic codas are dominated by scattered surface waves.
When efficient body wave to surface wave conversion mechanisms are present in the shallow crustal layers, such as soft sediment
layers, the scattered surface waves dominate the seismic coda at even early arrival times for shallow sources and at later
arrival times for deeper events. 相似文献
13.
新疆于田7.3级地震及部分强余震震源参数的重新测定 总被引：1，自引：1，他引：0
通过补充新疆、西藏和青海地震台网部分台站的地震波形资料,分别用不同地震定位方法,对2008年3月21日于田7.3级地震和最初的4个中强余震震源参数进行重新定位,并将其结果与地震目录结果和地震震相数据进行了分析与讨论。 相似文献
14.
地震之前长周期的地壳运动已为人们所关注,然而在零漂等问题尚未解决之前,长周期地震仪观测仍处于试验性阶段.另外,震前地气的喷溢和释放,只能在喷口处观测,距离稍远,就观测不到了,但由此而引起的大气振动和声学现象,却可在一定距离范围内观测到.因而可开展震前由长周期运动和地气等引起的大气声波、重力波等微气压波的观测研究.地震波所激发的次声[1],前人已有研究,但地震前的次声,中外文献还未见报道.1976年唐山地震后的1976年8月至1977年3月,笔者在北京首次开展微气压波的观测,发现了十余次地震前的微气压波,其特征为40—80秒的周期,1—5微巴的声压,波列很短,仅数分钟,出现于震前1—16小时.本文提出了识别震前微压波的分析方法,并讨论了其产生的可能机制和有关的临震现象. 相似文献
15.
The 10 January 2018 MW7.5 Swan island, Honduras earthquake occurred on the Swan island fault, which is a transform plate boundary between the North American and Caribbean plates. Here we back-project the rupture process of the earthquake using dense seismic stations in Alaska, and find that the earthquake ruptured at least three faults (three stages) for a duration of ~40 s. The rupture speed for the longest fault (stage 3) is as fast as 5 km/s, which is much faster than the local shear wave velocity of ~4 km/s. Supershear rupture was incidentally observed on long and straight strike-slip faults. This study shows a supershear rupture that occured on a strike-slip fault with moderate length, implying that supershear rupture might commonly occur on large strike-slip earthquakes. The common occurrence of supershear rupture on strike-slip earthquakes will challenge present understanding of crack physics, as well as strong ground motion evaluation in earthquake engineering. 相似文献
16.
Deterministic and probabilistic seismic hazard analyses should be complementary, in the sense that probabilistic analysis may be used to identify the controlling deterministic design‐level earthquake events, and more sophisticated models of these events may then be developed to account for uncertainties that could not have been included directly in the probabilistic analysis. De‐aggregation of the tentative uniform hazard spectra (UHS) in Hong Kong resulting from a probabilistic seismic hazard assessment (PSHA) indicates that strong and major distant earthquakes, rather than moderate local earthquakes, make the largest contribution to the seismic hazard level within the natural‐period range longer than 0.3 s. Ground‐motion simulations of controlling events located 90 and 340 km from Hong Kong, taking into account uncertainties in the rupture process, reveal that the tentative UHS resulting from the PSHA may have significantly underestimated the mid‐to‐long period components. This is attributed mainly to the adoption of double‐corner source‐spectrum models in the attenuation relationships employed in the PSHA. The results of the simulations indicate clearly that rupture directivity and rupture velocity can significantly affect the characteristics of ground motions, even from such distant earthquakes. The rupture‐directivity effects have profound implications in elongating the second corner period where the constant velocity intersects the constant displacement, thus increasing the associated displacement demand. However, demands for acceleration and velocity are found to be not sensitive to the presence of the directivity pulses. Ground pulses resulting from forward rupture directivity of distant earthquakes have longer predominant periods than the usual near‐fault directivity pulses. These long‐period pulses may have profound implications for metropolises, such as Hong Kong and others in Southeast Asia, having large concentration of high‐rise buildings. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
17.
J. M. Gómez B. Bukchin R. Madariaga E. A. Rogozhin B. Bogachkin 《Journal of Seismology》1997,1(3):219-235
The Susamyr earthquake of August 19, 1992 in Kyrgyzstan is one of the largest events (Ms = 7.4, Mb = 6.8) of this century in this region of Central Asia. We used broadband and long period digital data from IRIS and GEOSCOPE networks to investigate the source parameters, and their space-time distribution by modeling both body and surface waves. The seismic moment (M0 = 6.8 × 1019 N m) and the focal mechanism were determined from frequency-time analysis (FTAN) of the fundamental mode of long period surface waves (100–250 s). Then, the second order integral moments of the moment-rate release were estimated from the amplitude spectra of intermediate period surface waves(40–70 s). From these moments we determined a source duration of 11–13 s, major and minor axes of the source of 30 km and 10–22 km, respectively; and an instant centroid velocity of 1.2 km/s. Finally, we performed a waveform inversion of P and SH waves at periods from 5–60 s. We found a source duration of 18–20 s, longer than the integral estimate from surface wave amplitudes. All the other focal parameters inverted from body waves are similar to those obtained by surface waves ( = 87° ± 6°, = 49° ± 6°, = 105° ± 3°, h = 14 ± 2 km, and M0 = 5.8 ± 0.7 × 1019 N m). The initial rupture of this shallow earthquake was located at the south-west border of Susamyr depression in the western part of northern Tien Shan. A finite source analysis along the strike suggests a westward propagation of the rupture. The main shock of this event was preceded 2 s earlier by small foreshock. The main event was almost immediately followed by a very strong series of aftershocks. Our surface and body wave inversion results agree with the general seismotectonic features of the region. 相似文献
18.
The observation of the fault-zone trapped waves was conducted using a seismic line with dense receivers across surface rupture
zone of the M=8.1 Kunlun Mountain earthquake. The fault zone trapped waves were separated from seismograms by numerical filtering and spectral
analyzing. The results show that: a) Both explosion and earthquake sources can excite fault-zone trapped waves, as long as
they locate in or near the fault zone; b) Most energy of the fault-zone trapped waves concentrates in the fault zone and the
amplitudes strongly decay with the distance from observation point to the fault zone; c) Dominant frequencies of the fault-zone
trapped waves are related to the width of the fault zone and the velocity of the media in it. The wider the fault zone or
the lower the velocity is, the lower the dominant frequencies are; d) For fault zone trapped waves, there exist dispersions;
e) Based on the fault zone trapped waves observed in Kunlun Mountain Pass region, the width of the rupture plane is deduced
to be about 300 m and is greater than that on the surface.
Foundation item: Joint Earthquake Science Foundation of China (201001).
Contribution No. RCEG200305, Research Center of Exploration Geophysics, China Earthquake Administration. 相似文献
19.
The apparent horizontal propagation velocity, that is the propagation velocity of seismic waves with respect to the ground surface, is discussed in this paper. This parameter is needed to determine the effects of earthquakes on long structures such as bridges and buried pipelines as well as the torsional rotation of foundations of multi-storey buildings. A time window intensity tensor introduced by Penzien and Kubo is used herein to determine the predominant directions of ground motion during an earthquake. Considering the reflection of waves at a free surface, an approximate relationship between the predominant direction and the angle of incidence of body waves with respect to the ground surface is presented. Knowing the material properties of the top layer and the angle of incidence, the desired propagation velocity with respect to the ground surface is readily calculated. The median value of the apparent propagation velocity of shear waves for near field sites which recorded the 1971 San Fernando earthquake was determined to be about 2-1 km/s using the above method. A similar value for the 1979 Imperial Valley earthquake is 3·7 km/s. These values are consistent with the range of values for the apparent propagation velocity determined by other researchers. 相似文献
20.
2008年汶川特大地震中北川地区受灾特别严重,而该地区远离汶川主震震中超过100多千米.尽管汶川地震发生已近10年,但这种不正常现象一直困扰着地学工作者,至今没有给出合理的解答.为此,本文利用有限单元方法模拟汶川地震的主要发震断裂带（即：映秀—北川断层）的自发破裂动力学过程.模型中,几乎平直的映秀—北川断裂带在高川地区发生拐折,形成高川右弯.模拟结果显示,破裂沿着映秀—北川断裂带向东北方向前行,当破裂前端到达高川右弯时,破裂形态发生剧烈变化,破裂传播速度由亚剪切破裂突然转化为超剪切破裂.与断层阶区促进超剪切破裂明显不同的是,这种超剪切破裂形态的转化不需要时间停顿.由于超剪切地震破裂的产生,破裂辐射的地震波发生相长干涉,形成马赫波,地震动被大大放大.计算给出的强地面运动峰值加速度在北川地区不仅数值高,而且高值区分布范围广,造成了北川地区的震害特别严重.模拟结果还表明,若高川右弯不存在（即映秀—北川断层面为平直）,则北川地区的断层不会形成超剪切破裂;如果高川右弯附近断层的不连续程度较大,则破裂会被终止;这些情况下,北川地区的震害都没有那么严重.所以,高川右弯的几何形状对于超剪切破裂的形成起着决定性作用,也是造成远离震中的北川地区震害特别严重的主要原因.因此,分析发震断层几何对于研究震源动力学过程及震害评估等有着非常重要的科学意义和实际应用价值. 相似文献