Evaluation of liquefaction in Karasu River floodplain after the October 23, 2011, Van (Turkey) earthquake

Natural Hazards - The eastern shore of Lake Van was shaken by a powerful earthquake (M w 7.2) on October 23, 2011. The epicenter of the earthquake was located at about 30 km north of the...     

Measures for groundwater security during and after the Hanshin-Awaji earthquake (1995) and the Great East Japan earthquake (2011), Japan

Many big earthquakes have occurred in the tectonic regions of the world, especially in Japan. Earthquakes often cause damage to crucial life services such as water, gas and electricity supply systems and even the sewage system in urban and rural areas. The most severe problem for people affected by earthquakes is access to water for their drinking/cooking and toilet flushing. Securing safe water for daily life in an earthquake emergency requires the establishment of countermeasures, especially in a mega city like Tokyo. This paper described some examples of groundwater use in earthquake emergencies, with reference to reports, books and newspapers published in Japan. The consensus is that groundwater, as a source of water, plays a major role in earthquake emergencies, especially where the accessibility of wells coincides with the emergency need. It is also important to introduce a registration system for citizen-owned and company wells that can form the basis of a cooperative during a disaster; such a registration system was implemented by many Japanese local governments after the Hanshin-Awaji Earthquake in 1995 and the Great East Japan Earthquake in 2011, and is one of the most effective countermeasures for groundwater use in an earthquake emergency. Emphasis is also placed the importance of establishing of a continuous monitoring system of groundwater conditions for both quantity and quality during non-emergency periods.     

Simulation analysis of ground liquefaction induced by earthquake

A dynamic effective stress analysis with the finite element method has long been recommended to predict the liquefaction phenomena of sandy soil by authors and Zienkiewicz et al. as well as the similar approaches by the others. Our approach of the analysis is summarized in the first.

Until recently, however, these approaches has not commonly been used as the means of design, although its capability of prediction is appreciated by geotechnicians. This method has been neglected because of the lack of verification studies of soil models of sand and mathematical formulation for boundary problems of liquefaction phenomena. Therefore the verification of the numerical method to evaluate liquefaction potential are urgent requirement of the recent engineering practice. To respond this requirement, extensive numerical studies on the liquefation simulations are performed by DIANA program for shaking table tests which have been conducted by the authors. The test models are soil-structure type models with combination of homogenous ground and partially improved ground by compaction.

The good performance of our approach is proved by the results of numerical simulation showing good agreement with experimental data in terms of response acceleration, excess pore pressure, and deformation profile. It is also demonstrated that the numerical results can provide substantial information to understand the mechanisms of soil ground behavior which is not easily obtained by experiments.

The procedure to identify soil constants for the reflecting surface model is also reported in details.     

3-D GRACE gravity model for the 2011 Japan earthquake

The GRACE mission has contributed to the seismic characterization of major earthquakes in offshore regions of the world. Here, we isolate satellite gravity signal (μGal range) for the Japan Earthquake of 2011 using a difference method. Contrary to the existing gravity models, we propose a unit vertical pyramid based five-layer 3-D thrust fault model, which extends to the hypocenter and honors the ocean water layer and sea floor upheaval also. Our model partly uses existing seismological information (hypocenter depth of 32 km, rupture length of 300 km and vertical slip of 4 m), provides a snapshot of episodic subduction of the Pacific Plate below the Atlantic Plate and its gravity response closely matches the observed gravity (RMS error of 3.4012×10^?13μGal), fully accounting for co-seismic mass redistribution including sea surface deformation. Our inferred rupture length, rupture velocity, average seismic moment magnitude and momentum, respectively, are 300 km, 4.49 km/s, 1.152×10²¹?1.8816×10²¹ N m and 2.319×10⁶ GNs, which fairly agree with the literature. Further, our model inferred momentum at the sea floor corresponds to an area pulse that led to Tsunami generation.     

Modeling of strong motion generation areas of the 2011 Tohoku,Japan earthquake using modified semi-empirical technique

Modification in the semi-empirical technique for the simulation of strong ground motion has been introduced to incorporate the strong motion generation areas (SMGA) in the modeled rupture plane. Strong motion generation areas identified within the rupture plane of the Tohoku earthquake of March 11, 2011 (M _w = 9.0), have been modeled using this modified technique. Two different source models having four and five SMGAs, respectively, are considered for modeling purpose. Strong motion records using modified semi-empirical technique have been simulated at two near-field stations located at epicentral distance of 137 and 140 km, respectively, using two different source models. Comparison of the observed and simulated acceleration waveforms is made in terms of root mean square error (RMSE) at both stations. Minimum root mean square error of the waveform comparison has been obtained at both the stations for source model having five SMGAs. Simulations from same rupture model have been made at other four stations lying at epicentral distance between 154 and 249 km. Comparison of observed and simulated records has been made in terms of RMSE in acceleration records, velocity records and response spectra at each six station. Simulations have been made at six other stations to obtain distribution of peak ground acceleration and peak ground velocity with hypocentral distance. Peak ground acceleration and velocity from simulated and observed records are compared at twelve stations surrounding the source of Tohoku earthquake. Comparison of waveforms and parameters extracted from observed and simulated strong motion records confirms the efficacy of the developed modified technique to model earthquake characterized by SMGAs.     

Surface displacements in Japan before the 11 March 2011 M9.0 Tohoku-Oki earthquake

Daily resolution data retrieved from the 1243 ground-based Global Positioning System (GPS) stations in Japan are utilized to expose surface displacements before the destructive M9 Tohoku-Oki earthquake (March 11, 2011). Variations in the residual GPS data, in which effects of the long-term plate movements, short-term noise and frequency-dependent variations have been removed through a band-pass filter via the Hilbert–Huang transform, are compared with parameters of the focal mechanism associated with the Tohoku-Oki earthquake for validation. Analytical results show that the southward movements, which were deduced from the residual displacements and agree with the strike of the rupture fault, became evident on the 65th day before the Tohoku-Oki earthquake. This observation suggests that the shear stress played an important role in the seismic incubation period. The westward movements, which are consistent with the angle of the maximum horizontal compressive stress, covered entire Japan and formed an impeded area (142°E, 42°N) about 75 km away from the epicenter on the 47th day prior to the earthquake. The horizontal displacements integrated with the vertical movements from the residual GPS data are very useful to construct comprehensive images in diagnosing the surface deformation from destructive earthquakes along the subduction zone.     

Back-analysis of liquefaction in the 2006 Mozambique earthquake

A magnitude 7 earthquake occurred in southwest Mozambique in February 2006, triggering extensive liquefaction around the fault rupture. Samples were recovered from the liquefied soils for laboratory testing to calibrate a numerical model for the assessment of liquefaction susceptibility. Laboratory tests and simulations confirm that the alluvial sands from the area affected by the earthquake have a very high susceptibility to liquefaction, although this depends strongly on the in situ density, which is likely to be low since the soils are deposited in a major flood plain. Since many areas of Mozambique, including parts of the major coastal cities, are on similarly loose and saturated deposits, there could be a significant liquefaction hazard in future earthquakes.     

Probability of a great earthquake to recur off the pacific coast of central Japan

Probabilities of a great earthquake recurring in the Tokai district. Central Japan, are estimated on the basis of the statistical analysis of recurrence tendency and strain accumulation as monitored by geodetic surveys. Although probabilities thus estimated vary in a fairly wide range depending on data, attention should be paid to the fact that the probability of having a great earthquake within 10 years' time from 1977 is estimated as high as 30–50%.     

基于判别分析法的地震砂土液化预测研究

将距离判别分析方法应用于砂土液化的预测问题中,建立了砂土液化预测的距离判别模型。选用震级、研究深度、震中距、标贯击数、地下水位及地震持续时间等6项指标作为判别因子,以大量的工程实例数据作为学习样本进行训练,建立了线性判别函数对待评样本进行了评价。研究结果表明,距离判别分析模型判别砂土液化效果良好,预测准确度高,回判估计误判率低,可望成为砂土液化预测的有效手段。     

栗西沟尾矿坝地震响应及液化分析

采用不排水有效应力法,利用Geo-slope软件,对金堆城栗西沟尾矿坝进行了地震响应的综合分析与液化计算。结果显示: a .栗西沟尾矿坝在静态条件下是稳定的; b .在7度地震条件下,尾矿坝的加速度反应较小,其放大倍数为2.204; c .栗西沟尾矿坝内动剪应力和动孔压绝大部分是随着地震历时的增加而逐渐增大; d .坝内孔压比都较小,抗液化安全系数较大,但局部液化区的存在,仍可能影响到整个坝体的安全性,应在液化区采取加固措施。     

Explicit integration of bounding surface model for the analysis of earthquake soil liquefaction

This paper presents a new plasticity model developed for the simulation of monotonic and cyclic loading of non‐cohesive soils and its implementation to the commercial finite‐difference code FLAC, using its User‐Defined‐Model (UDM) capability. The new model incorporates the framework of Critical State Soil Mechanics, while it relies upon bounding surface plasticity with a vanished elastic region to simulate the non‐linear soil response. Stress integration of constitutive relations is performed using a recently proposed explicit scheme with automatic error control and substepping, which so far has been employed in the literature only for constitutive models aiming at monotonic loading. The overall accuracy of this scheme is evaluated at element level by simulating cyclic loading along complex stress paths and by using iso‐error maps for paths involving change of the Lode angle. The performance of the new constitutive model and its stress integration scheme in complex boundary value problems involving earthquake‐induced liquefaction is evaluated, in terms of accuracy and computational cost, via a number of parametric analyses inspired by the successful simulation of the VELACS centrifuge Model Test No. 2 studying the lateral spreading response of a liquefied sand layer. Copyright © 2009 John Wiley & Sons, Ltd.     

The large aftershocks triggered by the 2011 Mw 9.0 Tohoku-Oki earthquake,Japan

The Mw 9.0 Tohoku-Oki earthquake that occurred off the Pacific coast of Japan on March 11, 2011, was followed by thousands of aftershocks, both near the plate interface and in the crust of inland eastern Japan. In this paper, we report on two large, shallow crustal earthquakes that occurred near the Ibaraki-Fukushima prefecture border, where the background seismicity was low prior to the 2011 Tohoku-Oki earthquake. Using densely spaced geodetic observations (GPS and InSAR datasets), we found that two large aftershocks in the Iwaki and Kita-Ibarake regions (hereafter referred to as the Iwaki earthquake and the Kita-Ibarake earthquake) produced 2.1 m and 0.44 m of motion in the line-of-sight (LOS), respectively. The azimuth-offset method was used to obtain the preliminary location of the fault traces. The InSAR-based maximum offset and trace of the faults that produced the Iwaki earthquake are consistent with field observations. The fault location and geometry of these two earthquakes are constrained by a rectangular dislocation model in a multilayered elastic half-space, which indicates that the maximum slips for the two earthquakes are 3.28 m and 0.98 m, respectively. The Coulomb stress changes were calculated for the faults following the 2011 Mw 9.0 Tohoku-Oki earthquake based on the modeled slip along the fault planes. The resulting Coulomb stress changes indicate that the stresses on the faults increased by up to 1.1 MPa and 0.7 MPa in the Iwaki and Kita-Ibarake regions, respectively, suggesting that the Tohoku-Oki earthquake triggered the two aftershocks, supporting the results of seismic tomography.     

Effect of frequency-dependent radiation pattern in the strong motion simulation of the 2011 Tohoku earthquake,Japan, using modified semi-empirical method

We perform a strong ground motion simulation using a modified semi-empirical technique (Midorikawa in Tectonophysics 218:287–295, 1993), with frequency-dependent radiation pattern model. Joshi et al. (Nat Hazards 71:587–609, 2014) have modified the semi-empirical technique to incorporate the modeling of strong motion generation areas (SMGAs). A frequency-dependent radiation pattern model is applied to simulate high-frequency ground motion more precisely. Identified SMGAs (Kurahashi and Irikura in Earth Planets Space 63:571–576, 2011) of the 2011 off the Pacific coast of Tohoku earthquake (M _w  = 9.0) were modeled using this modified technique. We analyzed the effect of changing seismic moment values of SMGAs on the simulated acceleration time series. Final selection of the moment values of SMGAs is based on the root-mean-square error (RMSE) of waveform comparison. Records are simulated for both frequency-dependent and constant radiation pattern function. Simulated records for both cases are compared with observed records in terms of peak ground acceleration, peak ground velocity and pseudo-acceleration response spectra at different stations. Comparison of simulated and observed records in terms of RMSE suggests that the method is capable of simulating record, which matches in a wide frequency range for this earthquake and bears realistic appearance in terms of shape and strong motion parameters. The results confirm the efficacy and suitability of rupture model defined by five SMGAs for the developed modified technique.     

Long-traveling landslides in deep snow conditions induced by the 2011 Nagano Prefecture earthquake,Japan

Earthquakes in mountainous areas may produce many landslides that involve abundant snow, but few observations have been made of these hazardous phenomena. The 12 March 2011 north Nagano Prefecture earthquake (M_JMA 6.7) occurred in a mountainous part of Japan that typically has an annual snow cover of more than 2 m, and it induced many snowy landslides. Some of these traveled relatively long distances. We examined the snowy Tatsunokuchi landslide to reconstruct the landsliding processes over deep snow. We infer that the Tatsunokuchi landslide occurred by collapse of a rock debris mass of 5?×?10⁴ m³ that plunged into the abundant snow, forming a mixture of snow and rock debris, which then traveled on top of the snow. Later, the displaced mass included a large amount of snow which was pushed forward at the front and to the sides. The velocity of the landslide was estimated to be approximately 14 m/s. It appears that the displaced mass, having only a small proportion of rock debris, had a low enough density to travel easily on top of the snow. Our observations suggest that there was much liquid water at the base of the displaced mass shortly after the event. Our results suggest that landslides may damage wider areas than expected if they travel over deep snow.     

层间隔震地震响应分析

为了研究层间隔震结构的减震效果和变化规律,通过运用SAP2000大型有限元分析软件,在建立层间隔震结构的三维模型基础上,设置所在不同的隔震层位置,对所建隔震结构模型进行仿真分析。输入选定的不同地震波,通过结构模型进行分析对比,得出层间隔震结构的变化规律和减震效果,同时讨论不同位置的隔震层对结构变化规律和减震效果的影响,从而验证层间隔震的有效性。     

Regional differences in cognitive dissonance in evacuation behavior at the time of the 2011 Japan earthquake and tsunami

This paper constructs an evacuation decision-making model that takes cognitive dissonance into consideration. The purpose of this construction is to clarify the psychological mechanism for the evacuation behavior of residents during an emergency, based on Akerlof and Dickens (Akerlof and Dickens Am Econ Rev 72:307–319, 1982) "The economic consequences of cognitive dissonance". Specifically, we empirically explore people’s psychological mechanism (e.g., cognitive dissonance) for evacuation behavior when a tsunami disaster occurs. As a result, we show that the level of anxiety depends on the area where residents live and that the average anxiety of residents is mostly correlated with the level of damage of past disasters, and that it is affected also by the ages of residents. Since the level of anxiety largely affects an individual’s evacuation behavior, this result can indicate for what kinds of people intervention and assistance are required based on the level of anxiety. A high level of anxiety basically promotes evacuation. Since our results show that anxiety is increased by the experience of tsunamis, education having people virtually experience tsunamis may increase evacuation rates efficiently.

     

防水措施对堤坝地震液化影响的数值分析

通过基于有效应力的完全耦合动力分析方法,研究了混凝土面板坝在地震作用下的动力响应,详细地讨论了堤坝迎水面斜坡上铺设的防水毯对堤坝地震液化的影响。计算中土体采用Cyclic mobility本构模型,该模型通过在修正剑桥模型上增加应力诱导各向异性、超固结和结构性的概念及其相关发展准则,可以很好地描述可液化土体的动力特性。计算结果表明防水毯的存在可以有效降低坝体的地下水位浸润线,增加坝基的初始有效应力,从而降低坝基地震液化发生的可能性,同时坝体的变形明显减小。     

First-order rupture features of the 2011 MW 9.0 Tohoku (Japan) earthquake from surface waves

This study analyzed the rupture directivity of the 2011 Tohoku earthquake by using 100-s Rayleigh-wave travel-times, influenced by the finite source, to derive the fault parameters of the earthquake. The results demonstrated that the earthquake exhibited a slow rupture propagation with a rupture velocity of approximately 1.5–2.0 km/s and asymmetric bilateral faulting. The two rupture directions were N60°E and N127°E, with rupture lengths of approximately 276 km and 231 km, respectively. The rupture toward N60°E had a source duration of approximately 183 s, longer than that toward N127°E (approximately 156 s). Overall, the entire source duration of the earthquake faulting lasted approximately 183 s. Regarding historical seismicity in eastern Japan, the 2011 Tohoku earthquake not only ruptured a locked area in which large earthquakes have rarely occurred, but also ruptured the source regions of several historical earthquakes. With the exception of its slow rupture velocity and generation of a tsunami, the rupture features of the 2011 Tohoku earthquake were inconsistent with those of typical tsunami earthquakes.     

Impact of the 11 March 2011, Great East Japan earthquake and tsunami on the chemical industry

The Great East Japan earthquake and tsunami damaged or destroyed many industrial facilities housing or processing hazardous substances, such as refineries, petrochemical facilities and other types of chemical industry. This showed that also generally well prepared countries are at risk of suffering natural hazard triggered technological (Natech) accidents. An analysis of data collected from open sources and through interviews with authorities was performed to understand the main reasons for the industrial damage and downtime as well as the extent of hazardous-materials releases and the associated impact on society. The analysis of the data set confirmed the findings from other studies with respect to main damage and failure modes, as well as hazardous-materials release paths. In addition, gaps in Natech risk management were identified. Based on the data analysis and interviews lessons learned in support of a more far-reaching Natech risk management are presented.