Interrelation between seismicity parameters and delimiting potential seismic sources in a seismic statistical region and its influence on seismic risk estimation

In the paper, we have discovered the abnormal area distribution features of maximum variation values of ground motion parameter uncertainty with different probabilities of exceedance in 50 years within the range of 100°～120°E,29°～42°N for the purpose to solve the problem that abnormal areas of maximum variation values of ground motion parameter uncertainties emerge in a certain cities and towns caused by seismicity parameter uncertainty in a seismic statistical region in an inhomogeneous distribution model that considers tempo-spatial nonuniformity of seismic activity. And we have also approached the interrelation between the risk estimation uncertainty of a site caused by seismicity parameter uncertainty in a seismic statistical region and the delimitation of potential sources, as well as the reasons for forming abnormal areas. The results from the research indicate that the seismicity parameter uncertainty has unequal influence on the uncertainty of risk estimation at each site in a statistical region in the inhomogeneous distribution model, which relates to the scheme for delimiting potential sources. Abnormal areas of maximum variation values of ground motion parameter uncertainty often emerge in the potential sources of Mu≥8 (Mu is upper limit of a potential source) and their vicinity. However, this kind of influence is equal in the homogeneous distribution model. The uncertainty of risk estimation of each site depends on its seat. Generally speaking, the sites located in the middle part of a statistical region are only related to the seismicity parameter uncertainty of the region, while the sites situated in or near the juncture of two or three statistical regions might be subject to the synthetic influences of seismicity parameter uncertainties of several statistical regions.     

地震危险性分析中几个重要环节的关联性

为进一步揭示地震统计区划分、潜在震源区划分和地震活动性参数确定三者的关联性,在100deg;E～120deg;E和29deg;N～42deg;N范围内,寻找出21个位于不同位置、具有一定代表性的场点,研究在非均匀分布与均匀分布两种模型下,地震统计区活动性参数的不确定性对这些场点危险性估计的影响. 综合本次与以往的研究结果表明,不同的地震统计区划分方案会改变一个统计区所包含的地震资料,加上地震统计时段选取的不确定性,会导致统计区地震活动性参数估计的不确定性. 这种不确定性变化越大,均匀分布模型对场点危险性估计所产生的不确定影响也越大,也即地震统计区划分环节起主要作用. 在一个地震统计区内,划分潜在震源区和空间分布函数的不等权分配,提高了有可能发生大地震地方及其附近地区地震动参数的估计值. 在这些地方,潜在震源区划分不确定性的影响是很明显的,尤其对场点地震动参数（如烈度）绝对值的影响更为显著,也即潜在震源区划分环节起主要作用. 一般来说,潜在震源区划分环节的影响仅对最高和次高震级上限潜在震源区内的场点及最高震级上限潜在震源区附近的场点起主要作用,而对那些处于低震级上限潜在震源中的场点,则还是地震统计区划分不确定性的影响大于潜在震源区划分不确定性的影响.       

地震统计区活动性参数与潜在震源区划分的关联性及对危险性估计的影响

在考虑地震活动时空不均匀性的非均匀分布模型中, 就地震统计区活动性参数不确定性在某些城镇产生地震动参数不确定性最大变化值异常区的问题, 寻找出在100deg;~120deg;E、 29deg;～42deg;N范围内, 50年不同超越概率水平下地震动参数不确定性最大变化值异常区的分布特征. 探讨了地震统计区活动性参数不确定性引起的场点危险性估计不确定性与潜在震源区划分的关联性以及异常区产生的原因. 研究表明, 在非均匀分布模型中, 地震统计区活动性参数的不确定性对区内各场点危险性估计不确定的影响是不均衡的, 其与潜在震源区划分方案有关, 尤其在8级以上潜在震源区及其附近, 往往会出现地震动参数不确定性最大变化值的异常区. 而在均匀分布模型中, 统计区内活动性参数的不确定性对各场点的影响是均衡的, 各场点危险性估计的不确定性取决于场点的位置. 一般位于统计区中部的场点, 只与所在统计区的参数不确定性有关, 而位于或靠近不同统计区的交界处, 则可能同时受到几个统计区活动性参数不确定性的综合影响.     

Interrelation among strong earthquakes and its application in seismic hazard analysis

The intterrelation among strong earthquakes and its application are emphatically studied in this paper. Taking North China seismic region as study area, we have investigated how a great earthquake influence other strong earthqukaes in neighbouring area? Does there exist earthqukae immunity phenomenon? If it exists, what distributional pattern did it has in space-time domain? The results show that occurrence of earthquakes withM⩾7 has cetain immunity phenomenon to earthquakes withM⩾6 in North China. Among others, the immunity area of earthquakes withM=8 is much larger than that ofM=7. For earthquakes withM⩾8, the immunity area to the earthquakes ofM=7 is larger than toM=6. Based on the above analysis, using some statistical methods, we gave the variational regularity of seismic immunity factor with space and time, and explored its concrete application in seismic hazard analysis. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 339–346, 1993.     

青藏高原北部地区地震统计区划分及地震活动特征

地震统计区的划分是研究地震活动性的重要前提和基础,通过对青藏高原北部地区构造地质背景的分析,依据地球物理特征和强震活动特点,讨论和划分该区地震活动统计区,探讨研究区地震活动的复发特点、地震构造特征、潜在地震危险性及强度,分析研究区未来强震发生的强度和可能地点,结果表明,目前青藏高原北部地区处于第8个活跃期,仍存在发生强震的可能,且未来数年存在发生7级以上地震的可能,应密切东昆仑断裂带东段和祁连山中西段地区。     

Binomial model on seismic risk analysis

ＢｉｎｏｍｉａｌｍｏｄｅｌｏｎｓｅｉｓｍｉｃｒｉｓｋａｎａｌｙｓｉｓＪｉａｎＷＡＮＧ（王健）ａｎｄＺｈｅｎ－ＬｉａｎｇＳＨＩ（时振梁）（ＩｎｓｔｉｔｕｔｅｏｆＧｅｏｐｈｙｓｉｃｓ，ＳｔａｔｅＳｅｉｓｍｏｌｏｇｉｃａｌＢｕｒｅａｕ，Ｂｅｉｊｉｎｇ１００...     

沈北新区地震区划研究

以GB18306-2001《中国地震动参数区划图》的编制过程中的基础资料为基础,参照国际上最新地震区划原则,以抗倒塌参数作为基准,结合沈北新区及周边地区不同场地地震动参数,以及地震、地质背景的研究,编制了沈北新区地震区划。该地震区划可为沈北新区一般建设工程的抗震设防提供科学依据,本项研究也为同类项目的开展提供借鉴。     

Assessing current faulting behaviors and seismic risk of the Anninghe-Zemuhe fault zone from seismicity parameters

Introduction Strong and large earthquakes are prepared and generated on specific segments of active fault zones, especially on the asperity parts of the zones (Aki, 1984; Wiemer, Wyss, 1997; Wyss, et al, 2000). Therefore, both the faulting-behavior identification and the rupture segmentation mainly based on the method of active tectonics are always important aspects in active fault research (DING, et al, 1993). The purposes of the two aspects of research focus on determining fault units tha…     

新沂-泗县地震危险区地震活动和地震构造

运用深浅部构造对比研究、构造解析技术，结合历史地震资料、中强震观测资料分析、地震活动性分析结果，探讨中强震过渡区地震构造环境和地震韵律的研究途径，圈定出新沂—泗县地震危险区。对该危险区进行立体综合剖析，推演出未来中强震发生的空间部位，并预测了该区未来可能发生地震的震源深度、震级、地震长轴衰减方向、地震复发间隔等参数。     

Accounting for source location errors in the bayesian analysis of seismicity and seismic hazard

A method is presented for incorporating the uncertainties associated with hypocentral locations in the formulation of probabilistic models of the time and space distributions of the activity of potential seismic sources, as well as of the resulting seismic hazard functions at sites in their vicinity. For this purpose, a bayesian framework of analysis is adopted, where the probabilistic models considered are assumed to have known forms and uncertain parameters, the distribution of the latter being the result of an a priori assessment and its updating through the incorporation of the direct statistical information, including the uncertainty associated with the relations between the actual hypocentral locations and the reported data. This uncertainty is incorporated in the evaluation of the likelihood function of the parameters to be estimated for a given sample of recorded locations. For the purpose of illustration, the method proposed is applied to the modelling of the seismic sources near a site close to the southern coast of Mexico. The results of two alternate algorithms for the incorporation of location uncertainties are compared with those arising from neglecting those uncertainties. One of them makes use of Monte Carlo simulation, while the other is based on a closed-form analytical integration following the introduction of some simplifying assumptions. For the particular case studied, accounting for location uncertainties gives place to significant changes in the probabilistic models of the seismic sources. Deviations of the same order of magnitude can be ascribed to differences in the mathematical and/or numerical tools used in the uncertainty analysis. The resulting variability of the seismic hazard at the site of interest is less pronounced than that affecting the estimates of activity of individual seismic sources.     

1996年度地震危险区预测

总结１９９５年度的预报情况，提出了１９９６年度全国４个大区的地震活动性水平以及可能的危险地区。     

中强地震活动区地震年平均发生率确定方法的比较

目前确定地震活动性参数的方法有2种,即潜在震源区划分法和格点空间光滑法.本文针对格点空间光滑法,重点介绍了高斯空间光滑法及其改进后的方法,并对比分析了这些方法的优缺点及适用性;然后以华中为研究区,分别采用高斯空间光滑法和潜在震源区法建立地震活动性模型计算地震年平均发生率,并利用概率地震危险性分析方法计算地震危险性,对比两种方法所得区划结果的差异并分析了引起差异的原因.结果表明:空间光滑法适用于中强地震活动区地震危险性或由背景地震引起的地震危险性的计算;潜在震源区划分法适用于考虑明确的发震构造的地震危险性.将2种方法相结合,综合考虑地震和已知构造信息是判断中强地震活动区地震危险性的可行方法.     

Ambient tectonic shear stress field in Southern California and seismic hazard regions

ＡｍｂｉｅｎｔｔｅｃｔｏｎｉｃｓｈｅａｒｓｔｒｅｓｆｉｅｌｄｉｎＳｏｕｔｈｅｒｎＣａｌｉｆｏｒｎｉａａｎｄｓｅｉｓｍｉｃｈａｚａｒｄｒｅｇｉｏｎｓＰＥＩＳＨＡＮＣＨＥＮ（陈培善）ＬＥＩＸＩＡＯ（肖磊）ＴＯＮＧＸＩＡＢＡＩ（白彤霞）ＪＩＮＣＨ...     

潜在震源区震级上限不确定性研究

潜在震源区的震级上限（Mu）是指在该潜在震源区内可能发生的最大地震的震级．预期未来发生超过该震级地震的概率趋于0．本文运用误差分析及逻辑树等方法,并结合发震模型的数值模拟得到的大震合成目录等结果,系统分析并最终得到了不同途径给出的不同类型潜在震源区震级上限的不确定性．该结果可直接应用于包括地震区划在内的工程地震以及活动断裂危险性评价等工作中．     

Potential rupture surface model and its application on probabilistic seismic hazard analysis

Potential sources are simplified as point sources or linear sources in current probabilistic seismic hazard analysis (PSHA) methods. Focus size of large earthquakes is considerable, and fault rupture attitudes may have great influ-ence upon the seismic hazard of a site which is near the source. Under this circumstance, it is unreasonable to use the simplified potential source models in the PSHA, so a potential rupture surface model is proposed in this paper. Adopting this model, we analyze the seismic hazard near the Chelungpu fault that generated the Chi-Chi (Jiji) earthquake with magnitude 7.6 and the following conclusions are reached. 1 This model is reasonable on the base of focal mechanism, especially for sites near potential earthquakes with large magnitude; 2 The attitudes of poten-tial rupture surfaces have great influence on the results of probabilistic seismic hazard analysis and seismic zoning.     

Ambient tectonic shear stress field in Southern California and seismic hazard regions

According to the fracture mechanics rupture model of earthquakes put forward by us, several equations to compute tectonic ambient shear stress value τ₀ have been derived [equations (1), (2), (3), (5)]. τ₀ values for intermediate and small earthquakes occurred in Chinese mainland and Southern California have been calculated by use of these equations. The results demonstrate that the level and distribution of τ₀ are closely related to the location where large earthquakes will occur, i.e. the region with higher level of τ₀ will be prone to occur large earthquakes and the region with lower level will usually occur small earthquakes. According to the spatial distribution of τ₀, the seismic hazard regions or the potential earthquake source regions can in some degree be determined. According to the variation of τ₀ with time, the large earthquake occurrence time can be roughly estimated. According to the distribution of τ₀ in Southern California and variation with time, three high stress level regions are determined, one (Goldfield area) of them is the present seismic hazard region. Contribution No. 98A02023, Institute of Geophysics, State Seismological Bureau, China     

Parameter sensitivity analyses in seismic hazard

Ｐａｒａｍｅｔｅｒｓｅｎｓｉｔｉｖｉｔｙａｎａｌｙｓｅｓｉｎｓｅｉｓｍｉｃｈａｚ┐ａｒｄＪＩＡＮＷＡＮＧ（王健）ａｎｄＭＥＮＧ－ＴＡＮＧＡＯ（高孟潭）ＩｎｓｔｉｔｕｔｅｏｆＧｅｏｐｈｙｓｉｃｓ，ＳｔａｔｅＳｅｉｓｍｏｌｏｇｉｃａｌＢｕｒｅａｕ，Ｂｅ...     

山东某场地概率地震危险性分析

利用概率地震危险性分析(CPSHA)方法,对山东某场地进行地震危险性分析,通过对该场地划分潜在震源区,确定地震活动性参数及地震动衰减关系,计算分析地震危险性概率,基本确定对该场地地震动峰值加速度起主要贡献的几个潜在震源区及贡献值,并确定该场地50年超越概率10%的水平向基岩地震动加速度峰值。结果发现,CPSHA方法以具体的构造尺度和更加细致的构造标志来划分潜在震源区,使潜在震源区规模缩减,从而更能反映地震活动在空间分布上的不均匀性。     

Influence of uncertainty in delimitation of seismic statistical zone on results of PSHA

The seismic hazard of research area is evaluated by probabilistic analysis method for three different seismic statistical zone scenarios.The influence of uncertainty in seismic statistical zone delimiting on the evaluation result is discussed too.It can be seen that for those local sites along zone‘s border or within areas with vast change of upper bound magnitude among different scenarios the influence on seismic hazard result should not be neglected.     

河北平原地震带的现今活动性分析

根据近41年的现代地震资料,利用地震活动性参数组合、b值空间分布、断裂带分段,并结合历史强震构造背景的综合分析方法,分析河北平原地震带各分段现今地震活动习性和地震危险性.研究结果表明：河北平原地震带存在7个具有不同现今活动习性的分段,其中,唐山—迁安段和东明—阳谷段处于低b值、高应力状态,属于大震后晚期余震活跃或断层震后调整运动结果;昌平—宝坻、天津—肃宁段、新河段、邯郸—磁县及汤西段断层面现今活动习性均处于相对低应力下的频繁或稀疏小震滑动.因此,河北平原地震带未来短期内发生强震的可能性较小.