Statistical analysis of strong-motion accelerograms and its application to earthquake early-warning systems

In view of increasing damage due to earthquakes, and the current problems of earthquake prediction, real-time warning of strong ground motion is attracting more interest. In principle, it allows short-term warning of earthquakes while they are occurring. With warning times of up to tens of seconds it is possible to send alerts to potential areas of strong shaking before the arrival of the seismic waves and to mitigate the damage, but only if the seismic source parameters are determined rapidly. The major problem of an early-warning system is the real-time estimation of the earthquake's size.
We investigated digitized strong-motion accelerograms from 244 earthquakes that occurred in North and Central America between 1940 and 1986 to find out whether their initial portions reflected the size of the ongoing earthquake. Applying conventional methods of time-series analyses we calculate appropriate signal parameters and describe their uncertainties in relation to the magnitude and epicentral distance. The study reveals that the magnitude of an earthquake can be predicted from the first second of a single accelerogram within ±1.36 magnitude units. The uncertainty can be reduced to about ±0.5 magnitude units if a larger number (≥8) of accelerograms are available, which requires a dense network of seismic stations in areas of high seismic risk.     

A GIS-based approach to identify the spatial variability of social vulnerability to seismic hazard in Italy

This paper argues for a multidisciplinary framework to assess the relationship between environmental processes and social sciences that can be adapted to any geographic location. This includes both physical (earthquake hazard) and human (social vulnerability) dimensions in the context of disaster risk reduction. Disasters varies drastically depending on the local context. Indeed, the probability of a natural disaster having more devastating effects in one place than in another depends on the local vulnerability components of the affected society (cultural, social and economic). Therefore, there is an important correlation between the potential risk and the social resistance and resilience of a specific place, thus the disaster response varies according to the social fabric. In this context, the evaluation of social vulnerability is a crucial point in order to understand the ability of a society (studied at individual, household or community level) to anticipate, cope with, resist and recover from the impact of natural disaster events. Within this framework, the paper discusses how it is possible to integrate social vulnerability into the seismic risk analysis in Italy. Specifically, socioeconomic indicators were used to assess and mapping social vulnerability index. Afterwards, a Geographic Information System (GIS) approach was applied to identify the spatial variability of social vulnerability to seismic hazard. Through the use of a risk matrix, the classes of a social vulnerability index map were combined with those of a seismic hazard map proposed by INGV (National Institute of Geophysics and Volcanology). Finally, a qualitative social vulnerability exposure map to an earthquake hazard was produced, highlighting areas with high seismic and social vulnerability levels. Results suggest the importance of the integration of social vulnerability studies into seismic risk mitigation policies, emergency management and territorial planning to reduce the impact of disasters.     

地震灾害死亡人口快速评估方法对比研究

中国是世界上地震活动最为频繁的国家之一,属于地震多发区。在收集分析国内外关于地震灾害死亡人口评估模型的基础上,选取10种模型以2000年以来中国典型地震灾害为案例验证其适用性。结果表明：① 对于5.7级（含）以下地震,10种模型的评估结果基本都在合理范围内,可采用各评估结果的区间值来支撑应急决策;5.7~6.6级（含）地震,10种评估方法得到的结果表现出不同程度的偏差,可采用多数评估结果指向的死亡人口数量级来支撑应急决策;6.6级以上地震,则只能采用有特定适用范围的基于结构易损性的评估结果来支撑应急决策,且也存在较大的不确定性。② 从地震灾害人员伤亡动态评估方法、地震—地质灾害死亡人口快速评估方法和快速评估软件系统方面进行了相关讨论。此研究可为地震灾害死亡人口快速评估模型的改进与发展提供借鉴。     

A variational approach to elastic wave propagation in anomalous layers

Summary . A unified variational approach is derived for elastic wave propagation in infinite and semi-infinite stratified media involving anomalous layers. As a specific application we provide accurate approximations to the transition matrix which appears in the so-called amplification problem in earthquake engineering.     

The influence of earthquakes on the Chandler wobble during 1977–1983

Summary. A direct calculation is made of the effect on the Chandler wobble of 1287 earthquakes that occurred during 1977–1983. The hypocentral parameters (location and origin time) and the moment tensor representation of the best point source for each earthquake as determined by the 'centroidmoment tensor' technique were used to calculate the change in the Chandler wobble's excitation function by assuming this change is due solely to the static deformation field generated by that earthquake. The resulting theoretical earthquake excitation function is compared with the 'observed' excitation function that is obtained by deconvolving a Chandler wobble time series derived from LAGEOS polar motion data. Since only 7 years of data are available for analysis it is not possible to resolve the Chandler band and determine whether or not the theoretical earthquake excitation function derived here is coherent and in phase with the 'observed' excitation function in that band. However, since the power spectrum of the earthquake excitation function is about 56 dB less than that of the 'observed' excitation function at frequencies near the Chandler frequency, it is concluded that earthquakes, via their static deformation field, have had a negligible influence on the Chandler wobble during 1977–1983. However, fault creep or any type of aseismic slip that occurs on a time-scale much less than the period of the Chandler wobble could have an important (and still unmodelled) effect on the Chandler wobble.     

中国3A级及以上景区地震风险评估

中国的地震频率高,旅游景区分布广泛,地震的发生常常给震源附近的景区带来风险,景区的地震风险评估研究就尤为必要。在地震及风险相关理论研究和3A级及以上景区分布特征分析的基础上,利用地震动峰值加速度这一参数表征地震危险性,运用ArcGIS软件将地震动峰值加速度区划图和中国3A级及以上景区分布图叠加分析景区的暴露性,并采用风险评估的基本模型计算得到中国3A级及以上景区的地震风险评估结果。最终表明,从各省域的角度看,我国大部分地区的景区地震风险等级较低,江苏省、甘肃省景区地震风险较高,北京市景区地震风险最高。根据评估结果从三个角度分析了3A级及以上景区的地震风险分布态势并有针对性地提出应对策略。     

Low detection capability of global earthquakes after the occurrence of large earthquakes: investigation of the Harvard CMT catalogue

We investigated the detection capability of global earthquakes immediately after the occurrence of a large earthquake. We stacked global earthquake sequences after occurrences of large earthquakes obtained from the Harvard centroid-moment tensor catalogue, and applied a statistical model that represents an observed magnitude–frequency distribution of earthquakes to the stacked sequence. The temporal variation in model parameters, which corresponds to the detection capability of earthquakes, was estimated using a Bayesian approach. We found that the detection capability of global earthquakes is lower than normal for several hours after the occurrence of large earthquakes; for instance, the duration of lowered detection capability of global earthquakes after the occurrence of an earthquake with a magnitude of seven or larger is estimated to be approximately 12 hr.     

Surface-wave study of the Labrador Sea earthquake 1971 December

Source parameters of an earthquake that occurred on the continental slope off the coast of Labrador, the first earthquake known to have occurred in this region, are determined by using body-and surface-wave data. The focal mechanism is of the dip slip type and the focal depth is 16 km. The local deviatric stress field applied to the region is estimated to be compressional oriented normal to the North American continent. The observed surface-wave spectra are characterized by a sharp fall-off near the period T = 15–20 s. This observed fall-off is attributed to thick sediment at the continental slope. Consequently, when an earthquake is not located within a continental area, the source parameter determination using short-period surface waves is restricted in application.     

Detection of Damage due to Earthquake Using Mid-resolution Remotely Sensed Imageries

How to mitigate the loss of human being＇s life and properties is extremely important. Truly improvement of building structure is significant, but when a big earthquake occurs, disaster is unavoidable, so emergency response immediately after an earthquake plays a vital role. Traditional methods are time-consuming and laborious since almost everything is damaged after a big earthquake.     

帕米尔东北侧邻区第四纪新构造活动规律

帕米尔东北侧邻区新构造活动具有幅度巨大,阶段性继承性明显,现今活动性强烈等特点。以帕米尔高原隆升为背景,研究了帕米尔东北侧邻区的新构造运动及地震活动的规律,通过有限元数值模拟,分析了第四纪新构造活动的应力场,并进一步探讨了新构造运动与地震活动的力源机制。     

土壤可蚀性动态变化规律研究

通过回顾已有的研究成果，分析评价了现有具有代表性的土壤可蚀性评价指标的优缺点，提出了建立适用于土壤侵蚀预报的可蚀性评价指标的原则。并运用野外观测资料，计算分析了我国黑土、黄土，以及日本火山灰土等土壤可蚀性的季节变化规律，深入研究了土壤可蚀性随次降雨强度、不同强度段降雨组合的变化趋势。结果表明，单位降雨侵蚀力所对应的土壤流失量是反映土壤性质与流失量之间定量关系的最好指标，但不能把目前使用的土壤可蚀性指标直接移植于次降雨模型中。土壤可蚀性具有明显的季节变化，而其变化规律还存在地域差异性。采用最大30分钟雨强大于25－30mm/hr降雨的侵蚀产沙资料，计算的土壤可蚀性值比较稳定且接近该土类可蚀性的多年平均值。     

基于径流对气候变化敏感性指标的多源数据质量评估

准确评估径流对气候变化的敏感性对水资源管理至关重要。多源气象水文数据集已被广泛应用于径流对气候变化敏感性的分析中,但目前尚无研究从径流敏感性的角度评价不同数据集。基于中国6个不同气候条件流域的实测气象水文资料,本文计算了径流对降水和潜在蒸散发变化的敏感性,并以此为基准评估4类数据集GLDAS、ISIMIP2a、ISIMIP2b、CMIP6 共45套子数据集的径流敏感性模拟效果。结果表明：GLDAS数据集模拟精度较低,CMIP6、ISIMIP2a、ISIMIP2b数据集模拟精度差异较小;3套子数据集ISIMIP2a中的CLM4.0、CMIP6中的UKESM1-0-LL、MIROC6在6个流域均具有较好的径流敏感性模拟效果,可适用于不同气候条件下的径流敏感性模拟与演化趋势分析。本文研究结果可为气候变化影响下中国稀缺资料流域的径流和水资源变化预估提供参考。     

A comparison of scenario-based hybrid bilevel and multi-objective location-allocation models for earthquake emergency shelters: a case study in the central area of Beijing,China

The accurate location and allocation of disaster emergency shelters are key components of effective urban planning and emergency management. Various models have been developed to solve the location-allocation problem, but gaps remain with regard to model realism and associated applicability. For the available location and allocation models of earthquake emergency shelters, uncertainty with respect to earthquake hazard, population exposure, rate of damage to buildings and the effects of evacuee behavior are often neglected or oversimplified. Moreover, modifying the models can be an alternative means of improving the solution quality when the optimization algorithm has difficulty coping with a complex, high-dimensional problem. This article develops a scenario-based hybrid bilevel model that addresses the concerns related to high-dimensional complexity and provides a higher degree of realism by incorporating the uncertainties of population dynamics and earthquake damage scenarios into location-allocation problems for earthquake emergency shelters. A modified particle swarm optimization algorithm combined with a simulated annealing algorithm was applied to derive solutions using the hybrid bilevel model and a conventional multi-objective model, and the solutions obtained using the two models were then compared. The novel features of the study include the hybrid bilevel model that considers the dynamic number of evacuees and its implementation for earthquake emergency shelter location and allocation. The results show that the solutions significantly differ between daytime and nighttime. When applied to the multi-objective model, the optimization algorithm is time consuming and may only find the local optima and provide suboptimal solutions in the considered scenarios with more evacuees. By contrast, the hybrid bilevel model shows more desirable performance because it significantly reduces the dimensionality of the location-allocation problem based on a two-step-to-reach approach. The proposed hybrid bilevel model is proven to be useful for optimal shelter allocation, and the presented results can be used as a reference for balancing the interests of the government and residents during the planning of shelters in Beijing.     

地震灾害预测和应急模拟系统的设计与应用——以永安市城市应急系统为例

城市防震减灾是地震潜在频发区提高自然灾害防治能力建设的重要方面。本文结合福建省永安市城市防震减灾信息管理系统的建设,探讨设计防震减灾数值模型,分析模型集成的关键技术,构建了地震风险评估、建筑物易损性评价、生命与财产损失估算、救援与救灾管理调度等模型和基于GIS开发的震害预测和应急模拟系统。该系统在福建省永安市的实际应用表明,通过对地震灾害预测结果的分析,可加强城市抗震中的薄弱环节,为灾区政府应急响应和制订对策提供决策支持辅助信息,从而显著提高城市防震减灾的综合能力。     

深层地震勘探在深埋特长隧道勘察中的应用

以沪蓉国道主干线湖北省高坪一吉心段大水井隧道的工程地质勘察为例，讨论了深层地震勘探在深埋特长隧道勘察中的应用。利用深层地震反射波法可以有效地探测覆盖层、各风化层以及不同基岩界面的埋藏深度，根据波速判断隧道围岩类别、探测不良地质现象(喀斯特、断层、节理裂隙等)等。因此，深层地震勘探可为隧道的设计、施工提供必要的地质依据。     

A modified particle swarm optimization algorithm for optimal allocation of earthquake emergency shelters

Allocation for earthquake emergency shelters is a complicated geographic optimization problem because it involves multiple sites, strict constraints, and discrete feasible domain. Huge solution space makes the problem computationally intractable. Traditional brute-force methods can obtain exact optimal solutions. However, it is not sophisticated enough to solve the complex optimization problem with reasonable time especially in high-dimensional solution space. Artificial intelligent algorithms hold the promise of improving the effectiveness of location search. This article proposes a modified particle swarm optimization (PSO) algorithm to deal with the allocation problem of earthquake emergency shelter. A new discrete PSO and the feasibility-based rule are incorporated according to the discrete solution space and strict constraints. In addition, for enhancing search capability, simulated annealing (SA) algorithm is employed to escape from local optima. The modified algorithm has been applied to the allocation of earthquake emergency shelters in the Zhuguang Block of Guangzhou City, China. The experiments have shown that the algorithm can identify the number and locations of emergency shelters. The modified PSO algorithm shows a better performance than other hybrid algorithms presented in the article, and is an effective approach for the allocation problem of earthquake emergency shelters.     

宁夏引黄灌区蒸散发量的计算模拟

为了解宁夏引用耗排黄河水量的问题,针对水域、裸地-植被域和不透水域等不同土地利用类型,采用了Penman公式、Noilhan-Planton模型和Penman-Monteith公式等对相应土地利用类型的蒸散发量进行计算模拟,从而确定了区域蒸散发量的计算模拟方法。依据计算模拟结果和试验观测数据对区域蒸散发量的计算模拟方法进行了验证。基于以上研究,以宁夏引黄灌区为例,对宁夏引黄灌区2000年的蒸散发量和1991-2000年间蒸散发量的变化趋势进行了计算模拟,并就降雨量对区域蒸散发量的影响关系进行了分析。模拟结果表明,2000年宁夏引黄灌区(不计黄河干流河道本身的蒸发)的总蒸散发量为4.59×109m3,计入黄河干流河道本身的蒸发则总蒸散发量为4.97×109m3;1991-2000年10年间区域总蒸散发量和区域农田蒸散发量呈增加趋势,天然林草灌木地和荒地蒸散发量呈下降趋势;区域总蒸散发量、农田蒸散发量、林草灌木地蒸散发量等与降雨量有着较好的相关关系,并随着降雨量的增加呈递增趋势。     

The fractal geometry of the surface ruptures of the 1999 Chi-Chi earthquake, Taiwan

The 1999 September 20 Chi-Chi earthquake is the largest seismic event which occurred in the island during the twentieth century. Available seismic data relative to this earthquake are of high quality, and surface ruptures identified as features associated to the Chelungpu fault can be clearly observed at the surface and precisely mapped. We calculated the fractal dimension ( D ) and b value of Gutenberg–Richter law for 6-month aftershocks of the Chi-Chi earthquake for the fault area, and find that the surface ruptures exhibit self-similar geometry only within specific ruler intervals. The D values of the surface ruptures reflect the fault slip and geometry at depth. More importantly, the small-size aftershocks seem more likely to occur within high D value and high b value areas, whereas small D value and small b value areas have a high potential for medium- and large-size aftershocks.     

Simulating a seismic series using geostatistical and stochastic methods: application to the seismic series in the Alborán Sea (1997 June 24–?)

Seismic series can be taken as examples of correlated unstationary sets of time-stochastic sequences. We investigate the possibility of estimating what is most probable to occur subsequently, if we know the events that have occurred up to a given moment.
The stochastic methods can be used with data of the seismic series, irrespective of their genesis and origin. Using three stochastic methods, namely (1) simulating the likelihood of occurrence by conditional geostatistical simulation; (2) developing a stochastic analysis of the energy release by means of energy packages; and (3) calculating the occurrence time of the most probable next earthquake, we were able to simulate the occurrence of earthquakes that took place during the Alborán Sea seismic series (1997–1998).
We conclude that it is possible to set limits on the time of occurrence and energy release, understood as the magnitude of the most probable earthquake, during the development of a seismic sequence and prior to the actual occurrence of the earthquake.