智能辅助地震区划系统IASHES

本文概述了“场地地震危险度评估专家系统”课题组６年工作的主要成果和智能辅助地震区划系统ＩＡＳＨＥＳ的组成及测试结果，着重叙述了潜辰源区两级划分的思想，Ａ级潜在辰原区地震活动趋势估计和Ｂ级潜在震源区划分及震级上限判定所依据的专家知识，以及适用于专家系统的Ｂ级潜在震源区加权系数的确定方法。     

地震环境与潜在震源区信息系统的建立及应用

应用GIS建立的地震环境与潜在震源区信息系统是中国抗震设防区划图信息系统的一个子系统 ,其任务是为新一代区划图的编制及其它相关领域提供基础信息服务。该系统空间数据库包括地震地质、地球物理、地震活动性等基础资料以及地震区划的部分初步成果。系统以MapInfo桌面地图系统为软件开发及运行平台 ,采用公共识别码在属性数据和空间数据之间建立联系。实现了图形数据与属性数据的相互查询、指定区域查询、缓冲区查询及各种统计分析等功能 ;应用GIS软件的制图功能 ,实现了计算机制图 ;结合抗震减灾工作实践 ,建立了各种应用模型 ,初步实现了通过GIS动态反映地震环境的变化 ,为工程地震、地震预报等研究提供基础数据的目的     

张家口地区精细化地震灾害风险评估

本文从地震灾害、建筑物、人口、经济、抗震救灾等多方面出发,将自然属性与社会属性进行有效结合,对地震危险性、建筑物抗震性能等影响因素进行详细分析,构建城镇地震灾害风险评价指标体系,以张家口地区16个县区为例,采用专家-层次分析法,建立精细化地震灾害风险评估模型.研究结果表明,城镇建筑物抗震性能普遍较差,怀来县地震灾害风险...     

Three-dimensional nonlinear analysis for seismic soil–pile-structure interaction

A three-dimensional method of analysis is presented for the seismic response of structures constructed on pile foundations. An analysis is formulated in the time domain and the effects of material nonlinearity of soil on the seismic response are investigated. A subsystem model consisting of a structure subsystem and a pile-foundation subsystem is used. Seismic response of the system is found using a successive-coupling incremental solution scheme. Both subsystems are assumed to be coupled at each time step. Material nonlinearity is accounted for by incorporating an advanced plasticity-based soil model, HiSS, in the finite element formulation. Both single piles and pile groups are considered and the effects of kinematic and inertial interaction on seismic response are investigated while considering harmonic and transient excitations. It is seen that nonlinearity significantly affects seismic response of pile foundations as well as that of structures. Effects of nonlinearity on response are dependent on the frequency of excitation with nonlinearity causing an increase in response at low frequencies of excitation.     

The Principle and Method for Delineation of Potential Seismic Sources in Northwest Yunnan

INTRODUCTION Withrapideconomicdevelopment,deficiencyofelectricalpowerisbecomingincreasinglysevere.Therefore,theconstructionofmorehydropowerstationsinSouthwestChinawherehydropowerresources areabundantisinevitable.Presently,severalcascadepowerstationsarepla…     

Seismic Intensity Zoning Map of China (1990) and Its Explanation

The Seismic Intensity Zoning Map of China(1990)was based on the probabilistic method of seismic hazard analysis.In compiling the map,the characteristics of inhomogeneity of earthquake distribution both in space and time in China are considered sufficiently,and some necessary modifications in the model of seismic hazard analysis are carried out.Based on the analysis of the seismic activity and seismotectonic environment,26 seismic provinces are divided first as the statistical elements of the seismicity analysis; the seismic potential source areas are then divided in the seismic provinces.The 733 potential source areas with various upper limit magnitudes have been divided in the country.According to the reliable time domain of earthquake data with various magnitude intervals,the b values in magnitude-frequency relationship are calculated in the seismic provinces.According to the analysis of the inhomogeneity of seismicity distribution both in space and time,the annual average occurrence rates of the eart     

Characteristics of the Seismic Waves from a New Active Source Based on Methane Gaseous Detonation

Active seismic sources are critical for obtaining high resolution images of the subsurface. For active imaging in urban areas, environment friendly and green seismic sources are required. In present work, we introduce a new type of green active source based on the gaseous detonation of methane and oxygen. When fired in a closed container, the chemical reaction, i.e. gaseous detonation, will produce high pressure air over 150MPa. Seismic waves are produced when high pressure air is quickly released to impact the surroundings. The first field experiment of this active source was carried out in December, 2017 in Jingdezhen, Jiangxi Province, where a series of active sources were excited to explore their potential in mine exploration. In current work, we analyzed the seismic waves recorded by near-field accelerators and a dense short-period seismic array and compared them with those from a mobile airgun source, another kind of active source by releasing high pressure air into water. The results demonstrate that it can be used for high resolution near surface imaging. Firstly, the gaseous detonation productions are harmless CO₂ and water, making it a green explosive source. Secondly, the dominant seismic frequencies are 10-80Hz and a single shot can be recorded up to 15km, making it suitable for local structure investigations. Thirdly, it can be excited in vertical wells, similar to traditional powder explosive sources. It can also act as an additional on-land active source to airgun sources, which requires a suitable water body as intermediate media to generate repeating signals. Moreover, the short duration and high frequency signature of the source signals make it safe with no damage to nearby buildings. These make it convenient to excite in urban areas. As a new explosive source, the excitation equipment and conditions, such as gas ratio, sink depth and air-releasing directions, need further investigation to improve seismic wave generation efficiency.     

Confidence Evaluation of Medium-and Long-Term Earthquake Prediction by Use of the Analytical Hierarchy Process

This paper offers an approach to the relative confidence level of medium- and long-term earthquake prediction methods by use of the analytical hierarchy process (AHP). We construct the criterion judgment matrices according to the results of an expert questionnaire known as the Delphi scheme. From the matrices we can obtain a scale for the relative preference or priority weight of each factor. The quantitative weights might be applied to make synthetic prediction of earthquake risk areas in the northern part of the North China seismic region.     

Regional and local seismic hazard assessment

Recent earthquakes such as the M_JMA 7.2 Hyogo-ken Nambu earthquake and the M 7.4 Kocaeli earthquake demonstrate once again the need to include detailed soil investigation into hazard evaluation, that is the need of microzonation. Seismic hazard assessment evaluated at a regional scale generally does not consider soil effects but only in a limited way using an attenuation law that can be ‘soft soil’ or ‘rock’. However, the relevant role of seismic hazard in the assessment of seismic coefficients for the definition of the actions in seismic codes must be properly considered. That is to say, the level of protection of buildings is proportional to a definite level of hazard (generally considered to be the ground motion with 10% probability of exceedence in 50 years). When a microzonation is performed, this criterion cannot be ignored, therefore, a clear linkage must be established between hazard (regional scale) and microzonation. The crucial point is represented by the reference motion (or input motion) to be used for site effects analysis, that must be compatible with the regional seismic hazard. In this paper, three different approaches for reference motion evaluation are analysed: probabilistic; stochastic; and deterministic. Through the case history of Fabriano microzonation the three approaches are compared. It is shown that each approach presents advantages and disadvantages with respect to the others. For example, the probabilistic approach (the reference motion is directly derived from the expected response spectra for a given return period) is linked with hazard, but produces an overestimation in short periods range, while the deterministic approach correctly simulates the wave propagation, but it ends with a kind of conditional probability. Until now, clear criteria to choose the right approach do not appear to exist and the expert experience is of fundamental importance.     

紫坪铺水库地区蓄水前后视应力标度率变化研究

本文利用紫坪铺水库台网记录到的波形资料,计算了2004～2008年170个M_L≥1.0级地震的震源参数.紫坪铺水库震源参数计算结果与其他大陆地区有明显不同:(1)拐角频率远低于其他大陆地区结果,表明库区地震波传播经过了较强的衰减过程;(2)视应力计算结果比其他地区小3个数量级,可能是由于库区地震波的高频成分衰减强烈,低估了能量集中在高频的小地震的地震辐射能量.分析了蓄水前后拐角频率和地震矩以及视应力和地震矩关系(视应力标度率)变化,结果表明:相同地震矩的地震蓄水后拐角频率增加,地震高频成分相对丰富;蓄水前视应力与地震矩的关系不明显,蓄水后视应力随地震矩的增加而增加.视应力标度率的改变可能是蓄水后地震震源物理过程逐渐改变的直接反映.     

城市震害预测中设定地震的确定问题

提出了一个确定震害预测中设定地震的方法,包括：确定贡献量最大的潜在震源区、潜在震源区内贡献量最大的震级档和设定地震的构造位置等。以福建省泉州市为例,获得５０年超赵概率６３％、１０％和２％等３个概率水平下的设定地震。本文给出的设定地震方法纵使了确定论方法和概率论方法的优点,有助于地震危险性分析方法的发展。     

软土地基上地表建筑系统的强震反应

本文导出了一种给出相对烈度在lg R~0之间的收敛解(忽略震级)的小震方程式。结合在贝加尔地区岩石抗震特性调查与文字资料和统一理论,使人们可对震源等势面进行评估。确定了在震源区边界处的地震烈度稳定性和弹性波在地壳中的传播,使得推导出从地震主要参数震级向随震中距不同的烈度定量计算的转换成为可能。获得了烈度(能通量的密度)对距离的双线性相关,给出了能通量密度和相对烈度之间的关系。求出了取决于地表建筑地基的物理特性的振动载荷烈度。在地震学角度,这种强震的定量预测方法是一种提供详细地震区划和场地小区划的可能手段之一。     

地震前兆台网监测能力评估方法及其在首都圈地区的试用

简要介绍了地震前兆台网的前兆监测能力评估的二种方法,并在首都圈地区现今与未来监测能力评估中试用。评估的初步结果表明, 实施首都圈防震减灾示范区数字化前兆台网建设工程之后, 该区的地震前兆监测能力将得到显著增强, 但西南部和东北部山区仍然是源兆监测的“ 空白区”。     

Source parameters and scaling relationships in the Friuli-Venezia Giulia (Northeastern Italy) region

We estimated the source parameters of 53 local earthquakes (2.0<M_L<5.7) of the Friuli-Venezia Giulia (Northeastern Italy) area, recorded by the short-period local seismic network of the Istituto Nazionale di Oceanografia e Geofisica Sperimentale (OGS), in the period 1995-2003. Data were selected on the basis of high quality locations and focal mechanisms. Standard H/V spectral ratios (HVRS) of the three-component stations of the network were performed in order to assess local amplifications, and only stations showing HVRS not exceeding two were considered for the source parameters estimation. Both velocity and acceleration data were used to compute the SH-wave spectra. Observed spectra were corrected for attenuation effects using an independent regional estimate of the quality factor Q and a station dependent estimate of the spectral decay parameter k. Only earthquakes with M_L>3.0 recorded with a sampling rate of 125 cps were used to compute k, thus allowing to visualize a linear trend of the high frequency acceleration spectrum up to 40-50 Hz. SH-wave spectra, corrected for attenuation, showed an ω⁻² shape allowing a good fit with the Brune model. Seismic moments and Brune radii ranged between 1.5×10¹² and 1.1×10¹⁷  N m and between 0.1 and 2.7 km respectively. We obtained M_o=1.1×10¹⁷  N m for the seismic moment of the Kobarid (SLO) main shock, in good agreement with the Harvard CMT solution (M_o=3.5×10¹⁷  N m). Brune stress drops were confined to the range from 0.07 to 5.31 MPa, with an average value of 0.73 MPa and seem to be approximately constant over five orders of magnitude of seismic moment. Radiated seismic energy computed from two nearby stations scales with seismic moment according to , and apparent stress values are between 0.02 and 4.26 MPa. The observed scatter of Brune stress drop data allowed to hypothesize a scaling relation between seismic moment and corner frequency in order to accommodate both Brune stress drop and apparent stress scalings. No systematic differences are evidenced between stress parameters of earthquakes with different focal mechanisms. As a consequence, a relation of the seismic stress release with the strength of rocks can be hypothesized. A high correlation (r>0.9) of Brune stress drop is found with both apparent stress and RMS stress drop, according to and respectively.     

Seismic on floating ice: data acquisition versus flexural wave noise

Geophysical surveying of the Arctic will become increasingly important in future prospecting and monitoring of the terrestrial and adjacent areas in this hemisphere. Seismic data acquired on floating ice are hampered with extensive noise due to ice vibrations related to highly dispersive ice flexural waves generated by the seismic source. Several experiments have been conducted on floating ice in van Mijenfjorden in Svalbard in the Norwegian Arctic to specifically analyse the extent of flexural waves recorded with various seismic receivers and sources deployed both on top of ice and in the water below. The data show that flexural waves are severely damped at 5 m or deeper below the ice and hydrophone data suffer less from these vibrations compared with data recorded on the ice. Aliasing of single receiver hydrophone data can to some extent be suppressed using an in-line line source of detonating cord. Experiments on ice on shallow water show prominent guided wave modes often referred to as Scholte waves propagating along the seabed. In this case, both flexural and Scholte waves interfere and make a complicated pattern of coherent noise. On shallow water, the positioning and type of the seismic source must be evaluated with respect to the coherent noise generated by these waves. Geophone strings of 25 m effectively suppress both flexural and Scholte waves due to their relative short wavelengths. An airgun generates relative more low-frequency energy than a surface source of detonating cord. Accordingly, seismic mapping of deep seismic horizons seem to be best achieved using geophone strings of such length and an airgun source. For shallow targets, the use of hydrophones in combination with detonating cord is an appropriate solution. Seismic surveying in the Arctic always have to follow environmental restrictions of not disturbing or harming wildlife and not causing permanent footprints into the vulnerable tundra, which implies that the choice of seismic acquisition strategy might occur as a trade-off between optimum data quality and environmental constraints.     

南沙海域海底浅层第四系地震地层结构与地质意义

科技进步使得地震采集数据量及其精度实现质的飞跃,南沙海域的地震调查,采用国际先进水平的等离子震源,获得地震剖面精度优于3 m局部甚至可在1 m之内,为科学研究、工程、浅层资源、地质灾害预警等研究奠定基础.在南沙第四系识别出了七个地震反射界面,确定500 ms至海底沉积区间内地震层序与三期海平面升降并与冰期、间冰期对应,典型地震剖面展示第四纪至少有三套完整的具有三角洲顶积层、前积层、底积层的地震相证据,与全球的第四纪海平面的变化一致.精细的浅层地震结构表明：南沙的地质现象丰富,浅层断层非常发育,下切河谷、泥石流、滑坡等地质遗迹的形成的地震相清晰,是地质活动频繁的地区.     

ESEP3.0专家系统在新疆年度地震形势预测中的应用检验

使用2000—2003年度新疆地震局震情研究报告中的资料建立异常证据文件,应用ESEP3．0专家系统进行了推理预测,将其中的1年以内的预测意见与这4年新疆“震情研究报告”的预测意见及实际发生的地震情况进行了对比,并按中国地震局制定的“地震预报评分办法”进行了评分,最后认为：ESEP3．0专家系统目前可以用于新疆的年度地震趋势和地震危险区预测。     

天山地震带及乌恰交汇区强震活动特征

根据1880～1990年天山和乌恰地区M_s≥5.5级地震资料,分析讨论了研究区内各带强震活动的韵律特征和相关性、强震活动的整体迁移规律及环境因子与强震之间可能存在的某些内在联系。用信息熵和马尔柯夫方法对各地震带资料进行了统计计算。认为:在大区域构造应力场作用下,由于力源和构造环境的差异,造成区内应力场分布不均匀,应力在一定范围内变化、调整和传递,形成了各带地震活动在时间和空间分布上的差异。据此对整个天山地震带和乌恰区近期强震活动趋势作了判断。     

宁夏及其邻区地震活动带与小区域构造应力场

本文利用宁夏及其邻区地震台网记录的18099个初动符号,以单个地震震源机制解和小震综合解的平均解,求得7个小区的区域构造应力场。全区主压应力场的平均方位为39°左右。各小区的平均主压应力方位为:西(吉)、海(原)、固(原)地区60°;银川平原及石咀山地区42°;石咀山以北、以西地区26°;(中)卫、(中)宁地区17°。各区均以来自西南方向的压应力为主。并认为当弱震活动带走向与主压应力方位成25°—30°夹角时,未来在这些条带上发生中强地震的可能性较大     

Design,modelling and imaging of marine seismic swarm surveys

Autonomous marine vehicles instrumented with seismic sensors allow for new efficient seismic survey designs. One such design is the swarm survey, where a group, or swarm, of slow moving autonomous marine vehicles record seismic data from shots fired by a source vessel sailing around circles within the swarm. The size of the swarm is dictated by the maximum offset requirement of the survey, and it can be shaped to acquire wide‐ and full‐azimuth data. The swarm survey design equation describes the relationship between the source and receiver positions of the survey and the subsurface coverage or fold. It is used to adapt the swarm to the seismic survey requirements and to calculate survey duration time estimates as function of available equipment. It is shown that a survey conducted by a slowly moving swarm requires six times fewer shots than an equivalent seabed node survey conducted over 85.5 km². Swarm surveys can also be adapted to efficiently conduct infill surveys and replace multi‐vessel undershoots. The efficiency of the survey can further be increased when the autonomous marine vehicles are towing short streamers with multiple receivers. Synthetic tests show that the seismic images for swarm surveys are comparable to those from streamer surveys, while little variation in image quality is found when reducing the number of autonomous marine vehicles but equipping them with a short streamer with multiple receivers.