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1.
We examine the spatial distribution of earthquake hypocenters in four central California areas: the aftershock zones of the (1) 1984 Morgan Hill (2) 1979 Coyote Lake, and (3) 1983 Coalinga earthquakes, as well as (4) the aseismically creeping area around Hollister. The basic tool we use to analyze these data are frequency distributions of interevent distances between earthquakes. These distributions are evaluated on the basis of their deviation from what would be expected if earthquakes occurred randomly in the study areas. We find that both background seismic activity and aftershocks in the study areas exhibit nonrandom spatial distribution. Two major spatial patterns, clustering at small distances and anomalies at larger distances, are observed depending on tectonic setting. While both patterns are seen in the strike-slip environments along the Calaveras fault (Morgan Hill, Coyote Lake, and Hollister), aftershocks of the Coalinga event (a thrust earthquake) seem to be characterized by clustering only. The spatial distribution of earthquakes in areas gradually decreasing in size does not seem to support the hypothesis of a self-similar distribution over the range of scales studied here, regardless of tectonic setting. Spatial distributions are independent of magnitude for the Coalinga aftershocks, but events in strike-slip environments show increasing clustering with increasing magnitude. Finally, earthquake spatial distributions vary in time showing different patterns before, during, and following the end of aftershock sequences. 相似文献
2.
The macroseismic field of the Balkan area 总被引：1，自引：0，他引：1
A catalogue of 356 macroseimic maps which are available for the Balkan area was compiled, including information on the source parameters of the corresponding earthquakes, the macroseismic parameters of their strength and their macroseismic field. The data analysis of this catalogue yields new empirical relations for attenuation, which can be applied for the calibration of historical events, modelling of isoseismals and seismic hazard assessment. An appropriate analysis allowed the separation and estimation of the average values of the geometrical spreading, n, and anelastic attenuation factor, c, for the examined area which were found equal to –3.227 ± 0.112 and –0.0033 ± 0.0010. Scaling relations for the focal macroseismic intensity, If, and the epicentral intensity I0, versus the earthquake moment magnitude were also determined for each Balkan country. A gradual decrease of the order of 0.5 to 1 intensity unit is demonstrated for recent (after 1970) earthquakes in Greece. Finally the depths of the examined earthquakes as they robustly determined (error <5 km) on the basis of macroseismic data were found to have small values ( 10 km). However large magnitude earthquakes show higher focal depths ( 25 km), in accordance with an increase of the seismic fault dimensions for such events. 相似文献
3.
地震的等震线不仅反映了地震的大小,而且也反映了地震断层过程的类型和破裂速度.单侧破裂的断层过程呈现出蛋型的等震线,而双侧破裂的断层过程呈现出椭圆的等震线,等震线的长轴与短轴之比对于破裂传播速度十分敏感.本研究利用理论等震线与观测结果相比较的方法,确定了1964年日本新地震、1983年日本海中部地震、1975年中国海城地震和1976年中国唐山地震的破裂传播速度、断层类型以及断层走向.得到的断层破裂速度是剪切波的0.7——0.9倍.这些值比用长周期地震波所确定的要稍大.产生这种差异的原因是:对烈度起主要影响的短周期地震波强烈地依赖于小尺度的断层不均匀破裂过程,以及局部的破裂传播的开始和终止;而由长周期波所得到的破裂速度却反映了在整个断层上破裂传播的平均过程.根据等震线图所得出的断层类型及断层走向与其它独立方法的结果相一致.这意味着本方法可以应用于推断某些历史地震的断层类型、破裂传播速度及破裂传播方向. 相似文献
4.
Isoseismals of seismic intensity distributions are represented by earthquake source size, faulting mode, and rupture velocity of fault propagation. Unilateral faulting forms egg—shaped isoseimals, while bilateral faulting forms elliptical ones. It is found that the ratio of major to minor axes of isoseismals is sensitive to rupture velocity. Rupture velocity, faulting mode, and fault trend have been determined from the seismic intensity maps of the 1964 Niigata and the 1983 Japan Sea earthquakes in China by matching theoretical isoseismals. Rupture velocities thus estimated are mostly 70% to 90% of shear wave velocity. The difference would be considered as follows: short—waves which determine the seismic intensity are strongly dependent on the rupture of small—scale fault heterogeneities and on the jerky—onsets and abrupt terminations of local rupture propagations. On the other hand, rupture velocity from long—waves represents an average rupture propagation along the whole fault length. Faulting mode and fault trend estimated from seismic intensity maps match with each earthquake faulting independently determined. This suggests that the present method would be applicable to some historical earthquakes with known seismic intensity distribution to obtain detailed information on the faulting process. 相似文献
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Tiziana Tuvè Antonio Teramo Jesus Ibañez Carla Bottari Domenica Termini 《Pure and Applied Geophysics》2005,162(4):747-760
A modelling of the observed macroseismic intensity of historical and instrumental earthquakes in southern Spain is proposed, with the aim of determining the macroseismic parameters for seismic hazard evaluation in a region in which the characterization of intensity distribution of seismic events shows different levels of difficulty referable to the complex faults system of the area in study. The adopted procedure allows an analytical determination of epicenters and principal attenuation directions of earthquakes with a double level of verification with reference to the maximum shaking area and structural lineaments of the region, respectively. The analyses, carried out on a suitable number of events, highlight, therefore, some elements for a preliminary characterization of a seismic zonation on the basis of the consistency between seismic intensity distribution of earthquakes and corresponding structural framework. 相似文献
6.
Ch. Kkallas C. B. Papazachos D. Boore Ch. Ventouzi B. N. Margaris 《Bulletin of Earthquake Engineering》2018,16(11):5121-5150
We model the macroseismic damage distribution of four important intermediate-depth earthquakes of the southern Aegean Sea subduction zone, namely the destructive 1926 M?=?7.7 Rhodes and 1935 M?=?6.9 Crete earthquakes, the unique 1956 M?=?6.9 Amorgos aftershock (recently proposed to be triggered by a shallow event), and the more recent 2002 M?=?5.9 Milos earthquake, which all exhibit spatially anomalous macroseismic patterns. Macroseismic data for these events are collected from published macroseismic databases and compared with the spatial distribution of seismic motions obtained from stochastic simulation, converted to macroseismic intensity (Modified Mercalli scale, IMM). For this conversion, we present an updated correlation between macroseismic intensities and peak measures of seismic motions (PGA and PGV) for the intermediate-depth earthquakes of the southern Aegean Sea. Input model parameters for the simulations, such as fault dimensions, stress parameters, and attenuation parameters (e.g. back-arc/along anelastic attenuation) are adopted from previous work performed in the area. Site-effects on the observed seismic motions are approximated using generic transfer functions proposed for the broader Aegean Sea area on the basis of VS30 values from topographic slope proxies. The results are in very good agreement with the observed anomalous damage patterns, for which the largest intensities are often observed at distances >?100 km from the earthquake epicenters. We also consider two additional “prediction” but realistic intermediate-depth earthquake scenarios, and model their macroseismic distributions, to assess their expected damage impact in the broader southern Aegean area. The results suggest that intermediate-depth events, especially north of central Crete, have a prominent effect on a wide area of the outer Hellenic arc, with a very important impact on modern urban centers along northern Crete coasts (e.g. city of Heraklion), in excellent agreement with the available historical information. 相似文献
7.
Ground motion prediction equations (GMPE) in terms of macroseismic intensity are a prerequisite for intensity-based shake
maps and seismic hazard assessment and have the advantage of direct relation to earthquake damage and good data availability
also for historical events. In this study, we derive GMPE for macroseismic intensity for the Campania region in southern Italy.
This region is highly exposed to the seismic hazard related to the high seismicity with moderate- to large-magnitude earthquakes
in the Appenninic belt. The relations are based on physical considerations and are easy to implement for the user. The uncertainties
in earthquake source parameters are accounted for through a Monte Carlo approach and results are compared to those obtained
through a standard regression scheme. One relation takes into account the finite dimensions of the fault plane and describes
the site intensity as a function of Joyner–Boore distance. Additionally, a relation describing the intensity as a function
of epicentral distance is derived for implementation in cases where the dimensions of the fault plane are unknown. The relations
are based on an extensive dataset of macroseismic intensities for large earthquakes in the Campania region and are valid in
the magnitude range M
w = 6.3–7.0 for shallow crustal earthquakes. Results indicate that the uncertainties in earthquake source parameters are negligible
in comparison to the spread in the intensity data. The GMPE provide a good overall fit to historical earthquakes in the region
and can provide the intensities for a future earthquake within 1 intensity unit. 相似文献
8.
In the process of updating existing PSHA maps in Central Asia, a first step is the evaluation of the seismic hazard in terms of macroseismic intensity by applying a data driven method. Following the Site Approach to Seismic Hazard Assessment (SASHA) [11], the evaluation of the probability of exceedance of any given intensity value over a fixed exposure time, is mainly based on the seismic histories available at different locations without requiring any a-priori assumption about seismic zonation. The effects of earthquakes not included in the seismic history can be accounted by propagating the epicentral information through a Intensity Prediction Equation developed for the analyzed area. In order to comply with existing building codes in the region that use macroseismic intensity instead of PGA, we evaluated the seismic hazard at 2911 localities using a macroseismic catalog composed by 5322 intensity data points relevant to 75 earthquakes in the magnitude range 4.6–8.3. The results show that for most of the investigated area the intensity having a probability of at least 10% to be exceeded in 50 years is VIII. The intensity rises to IX for some area struck by strong earthquakes in the past, like the Chou-Kemin-Chilik fault zone in northern Tien-Shan, between Kyrgyzstan and Kazakhstan, or in Gissar range between Tajikistan and Uzbekistan. These values are about one intensity unit less than those evaluated in the Global Seismic Hazard Assessment Program (GSHAP; Ulomov, The GSHAP Region 7 working group [29]). Moreover, hazard curves have been extracted for the main towns of Central Asia and the results compared with the estimates previously obtained. A good agreement has been found for Bishkek (Kyrgyzstan) and Dushanbe (Tajikistan), while a lower probability of occurrence of I=VIII has been obtained for Tashkent (Uzbekistan) and a larger one for I=IX in Almaty (Kazakhstan). 相似文献
9.
Broadband ground motion simulation using a hybrid approach of the May 21, 2021 M7.4 earthquake in Maduo,Qinghai, China 
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下载免费PDF全文 Yijun Liu Xiaofen Zhao Zengping Wen Jie Liu Bo Chen Chunyao Bu Chao Xu 《地震科学（英文版）》2023,36(3):175-199
In this study, the broadband ground motions of the 2021 M7.4 Maduo earthquake were simulated to overcome the scarcity of ground motion recordings and the low resolution of macroseismic intensity map in sparsely populated high-altitude regions. The simulation was conducted with a hybrid methodology, combining a stochastic high-frequency simulation with a low-frequency ground motion simulation, from the regional 1-D velocity structure model and the Wang WM et al. (2022 ) source rupture model, respectively. We found that the three-component waveforms simulated for specific stations matched the waveforms recorded at those stations, in terms of amplitude, duration, and frequency content. The validation results demonstrate the ability of the hybrid simulation method to reproduce the main characteristics of the observed ground motions for the 2021 Maduo earthquake over a broad frequency range. Our simulations suggest that the official map of macroseismic intensity tends to overestimate shaking by one intensity unit. Comparisons of simulations with empirical ground motion models indicate generally good consistency between the simulated and empirically predicted intensity measures. The high-frequency components of ground motions were found to be more prominent, while the low-frequency components were not, which is unexpected for large earthquakes. Our simulations provide valuable insight into the effects of source complexity on the level and variability of the resulting ground motions. The acceleration and velocity time histories and corresponding response spectra were provided for selected representative sites where no records were available. The simulated results have important implications for evaluating the performance of engineering structures in the epicentral regions of this earthquake and for estimating seismic hazards in the Tibetan regions where no strong ground motion records are available for large earthquakes. 相似文献
10.
As large destructive seismic events are not frequent in Algeria, anexhaustive knowledge of the historical seismicity is required to have arealistic view of seismic hazard in this part of the world. This research workpresents a critical reappraisal of seismicity in the north-eastern Algeria forseismotectonic and seismic hazard purposes. This part of work focuses onthe seismicity of pre-1900 period for the area under consideration[33°N-38°N, 4°E-9.5°E]. By going back tothe available documentary sources and evaluating and analysing the eventsin geographical, cultural and historical context, it has been possible toidentify 111 events, from 1850–1899, which are not reported in therecent Algerian catalogue. Several spurious events, reported in standardlistings, have been deleted and nine unknown events have been discovered.It is quite clear that macroseismic information derived from press reportsand published documents in Algeria, under certain conditions, is veryincomplete, even for destructive earthquakes, located in the countrysideaway from communication centres. One of the reasons for this iscensorship, noticeable during the colonisation period. Critical analysis ofnewly collected information has allowed the determination and/or theimprovement of the macroseismic parameters of each event, such aslocation, maximum epicentral intensity and magnitude to produce anearthquake catalogue as homogeneous and complete as the available data,for the zone under study. The criteria used in this research are explainedand eight historical earthquakes have been the subject of retrospectivemacroseismic field construction.The investigation of historical earthquakes is one of the most important taskin studying seismotectonic for seismic hazard evaluation purposes. 相似文献
11.
This study analyses the performance of residential buildings in the town of Hveragerði in South Iceland during the 29 May 2008 Mw 6.3 Ölfus Earthquake. The earthquake occurred very close to the town, approximately 3–4 km from it. Ground shaking caused by the earthquake was recorded by a dense strong-motion array in the town. The array provided high-quality three-component ground acceleration data which is used to quantify a hazard scenario. In addition, surveys conducted in the town in the aftermath of the earthquake have provided information on macroseismic intensity at various locations in the town. Detailed information regarding the building stock in the town is collected, and their seismic vulnerability models are created by using building damage data obtained from the June 2000 South Iceland earthquakes. Damage to buildings are then simulated by using the scenario hazard and vulnerability models. Damage estimates were also obtained by conducting a survey. Simulated damage based on the scenario macroseismic intensity is found to be similar to damage estimated from survey data. The buildings performed very well during the earthquake—damage suffered was only 5 % of the insured value on the average. Correlation between actual damage and recorded ground-motion parameters is found to be statistically insignificant. No significant correlation of damage was observed, even with macroseismic intensity. Whereas significant correlation was observed between peak ground velocity and macroseismic intensity, neither of them appear to be good indicators of damage to buildings in the study area. This lack of correlation is partly due to good seismic capacity of buildings and partly due to the ordinal nature of macroseismic intensity scale. Consistent with experience from many past earthquakes, the survey results indicate that seismic risk in South Iceland is not so much due to collapse of buildings but rather due to damage to non-structural components and building contents. 相似文献
12.
Vera D’Amico Dario Albarello Ragnar Sigbjörnsson Rajesh Rupakhety 《Bulletin of Earthquake Engineering》2016,14(7):1797-1811
We present the results of probabilistic seismic hazard assessment for Iceland in the framework of the EU project UPStrat-MAFA using the so-called site approach implemented in the SASHA computational code. This approach estimates seismic hazard in terms of macroseismic intensity by basically relying on local information about documented effects of past seismic events in the framework of a formally coherent and complete treatment of intensity data. In the case of Iceland, due to the lack of observed intensities for past earthquakes, local seismic histories were built using indirect macroseismic estimates deduced from epicentral information through an empirical attenuation relationship in probabilistic form. Seismic hazard was computed for four exceedance probabilities for an exposure time of 50 years, equivalent to average return periods of 50, 200, 475 and 975 years. For some localities, further return periods were examined and deaggregation analysis was performed. Results appear significantly different from previous seismic hazard maps, though just a semi-qualitative comparison is possible because of the different shaking measure considered (peak ground acceleration versus intensity), and the different computational methodology and input data used in these studies. 相似文献
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14.
本文基于Haskell的3源辐射谱模型,加上介质非弹性吸收项,几何扩散项和自由面放大效应,推演出峰值加速度和均方根加速度表达式。据此,建议一种考虑震源破裂方向的地震动衰减模型。用Morgan Hill和Imperial Valley两地震的峰值加速度资料,单震级统计分析结果表明,文中建议的地震动衰减模型是合理的。与Joyner和Boore所用的衰减模型相比较,剩余标准差可减少0.1——0.2。本文所考虑的震源破裂的地震动衰减模型,可分别用于不同断层类型的地震,如单侧和双侧走滑型地震及倾滑型地震,分别建立地震动衰减关系,进行地震危险性分析。文章最后给出了美国西部考虑震源破裂方向的地震动峰值加速度和均方根加速度的衰减关系。 相似文献
15.
地震破裂区是地震时沿发震断裂带的同震错动面或破裂面在地表的垂直投影区域,指示了震源断层/破裂的位置与尺度。确定过去长期的强震/大地震破裂区是鉴别地震空区、研究与预测强震危险性的重要基础。对于现代强震,破裂区可运用多种现代技术方法确定,但对于历史强震,破裂区确定的方法需要探索与发展。以华北地区为例,研究利用烈度/等震线资料、结合地震构造与震区地表地质环境等信息确定历史强震破裂区的方法,并开展应用试验。结果表明:研究区现代地震破裂区延伸的烈度区间与极震区烈度、震区环境之间存在密切关系,基于这种关系建立了2条经验准则,可分别用于根据烈度分布确定华北2类震区环境(基岩区和厚层第四纪松散堆积覆盖区)历史强震破裂区的位置与延伸。文中还提出通过综合地震构造、现代小震/余震分布等信息,辅助确定历史强震破裂区横向宽度的思路与途径。作为应用试验,文中确定了5次历史地震的破裂区,结果表明本文发展的经验准则及相应方法适用于华北地区历史强震破裂区的确定。 相似文献
16.
A procedure is proposed for the reconfiguration of the macroseismic planes relative to earthquakes that, being characterized by a reduced number of points of observed intensity due to a lack of information, or having the epicenter very close to the coastline, are characterized by an incomplete distribution of observed intensity levels. The design of a plurality of virtual areas, through which a distribution of intensity consistent with an anisotropic model of attenuation is depicted, allows a reliable determination of macroseismic parameters of the same seismic event. 相似文献
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Paola Traversa David Baumont Kévin Manchuel Emmanuelle Nayman Christophe Durouchoux 《Bulletin of Earthquake Engineering》2018,16(6):2169-2193
The estimation of the seismological parameters of historical earthquakes is a key step when performing seismic hazard assessment in moderate seismicity regions as France. We propose an original method to assess magnitude and depth of historical earthquakes using intensity data points. A flowchart based on an exploration tree (ET) approach allows to apply a consistent methodology to all the different configurations of the earthquake macroseismic field and to explore the inherent uncertainties. The method is applied to French test case historical earthquakes, using the SisFrance (BRGM, IRSN, EDF) macroseismic database and the intensity prediction equations (IPEs) calibrated in the companion paper (Baumont et al. Bull Earthq Eng, 2017). A weighted least square scheme allowing for the joint inversion of magnitude and depth is applied to earthquakes that exhibit a decay of intensity with distance. Two cases are distinguished: (1) a “Complete ET” is applied to earthquakes located within the metropolitan territory, while (2) a “Simplified ET” is applied to both, offshore and cross border events, lacking information at short distances but disposing of reliable data at large ones. Finally, a priori-depth-based magnitude computation is applied to ancient or poorly documented events, only described by single/sporadic intensity data or few macroseismic testimonies. Specific processing of “felt” testimonies allows exploiting this complementary information for poorly described earthquakes. Uncertainties associated to magnitude and depth estimates result from both, full propagation of uncertainties related to the original macroseismic information and the epistemic uncertainty related to the IPEs selection procedure. 相似文献
19.
An evaluation of the magnitude of historical earthquakes is proposed, through an empirical relation based on a felt area of historical earthquakes derived from a vectorial modelling of macroseismic intensity distribution. 相似文献