基于GeoClaw海啸数值模拟程序对2011年日本东北大地震有限断层模型的验证

由于海啸波具有长周期、慢衰减的特征,对于能够激发海啸的海底地震,海啸波资料一定程度上可以作为利用地震波资料和大地测量资料反演得到的震源有限断层模型的补充数据,以验证该模型的合理性.本文以2011年日本东北大地震海啸期间反演的震源模型为例,利用Okada弹性半无限空间理论将震源有限断层模型转化为垂向海底变形;然后利用Ge...     

考虑竖向地震作用的振动控制及其优化研究

目前,MRD结构的分析通常只考虑水平地震动而不考虑竖向地震动的影响,地面的水平运动和竖向运动具有相关性,从而影响控制效果．因此对双向地震耦合作用下MRD结构的理论进行研究,建立动力分析模型并得出运动微分方程．以8层MRD结构为例进行地震反应分析,研究表明,考虑和不考虑竖向地震作用,MRD对结构均有良好的控制作用,但是竖向地震作用的存在,使结构各层的层间位移峰值有不同程度的增加,其增量随着竖向地震作用的增加而增加,因此建议在高烈度地区的建筑物考虑竖向地震作用对结构的影响．建立MRD结构优化设计模型,采用IHGA程序对结构进行优化设计．结果表明, MRD结构在各种工况下的各项地震反应均得到更好的控制．     

The diversity of the physics of earthquakes

Earthquakes exhibit diverse characteristics. Most shallow earthquakes are “brittle” in the sense that they excite seismic waves efficiently. However, some earthquakes are slow, as characterized by tsunami earthquakes and even slower events without any obvious seismic radiation. Also, some earthquakes, like the 1994 Bolivian deep earthquake, involved a large amount of fracture and thermal energy and may be more appropriately called a thermal event, rather than an earthquake. Some earthquakes are caused by processes other than faulting, such as landslides. This diversity can be best understood in terms of the difference in the partition of the released potential energy to radiated, fracture, and thermal energies during an earthquake. This approach requires detailed studies on quantification of earthquakes and estimation of various kinds of energies involved in earthquake processes. This paper reviews the progress in this field from historical and personal points of view and discusses its implications for earthquake damage mitigation.     

An application of Bayesian (ABIC) smoothing methods to estimating space and time variations in the magnitude distributions of earthquakes

On the basis of Akaike's Bayesian information criterion (ABIC), a new method of estimating temporal and spacial variations in the magnitude-frequency relation (b value) is developed. The space-time volume studied is divided into a number of segments having equal volume, for which b values are estimated. The smoothness of the estimated b value is guaranteed by the introduction of a prior distribution. The parameters of the prior distribution are chosen in such a way as to minimize the ABIC. This method is employed to study the temporal and spatial variations of b values for microearthquake activity in the Kanto, Tokai and Tottori areas, where seven earthquakes having magnitudes of M6.0 and larger have recently taken place. States of temporal variations of b values are classified into three groups; increase, decrease and nochange. The space-time volume of decrease accounts for approximately 10% of the total volume. For a period before the occurrence of earthquakes, the decrease appears more frequently than might be expected. It is concluded that the decrease in the b value is a promising candidate to act as a precursory phenomena.This work was carried out under the ISM Cooperative Research Program (88-ISM CRP-60).     

Cyclic strength of imperfectly saturated sands and analysis of liquefaction

The simplified method of analysis to assess liquefaction potential of a given sand deposit is briefly introduced in the first part of this paper. Then, recent advances in the laboratory testing for evaluating liquefaction resistance are described with a particular emphasis on the sand partly saturated with water. As a means to identify the degree of saturation which is applicable for both field deposits and laboratory samples, the use of the longitudinal wave (P-wave) is proposed based on a suite of data obtained from the triaxial tests in the laboratory. It is recommended that the non-destructive P-wave measurements be carried out first to determine the degree of saturation, and then the cyclic triaxial tests involving large destructive strains should be performed to determine the cyclic strength on the same sample of the sand. In order to demonstrate usefulness of the proposed approach, two sets of undisturbed samples were secured from two sites; one is located in Sakai-minato city which has suffered severe liquefaction at the time of the 2000 Tottoriken-Seibu earthquake and the other site is located in Koshigaya city, Saitama, where likelihood of liquefaction to occur in a future earthquake is of major concern. Penetration tests and in-situ velocity logging were also conducted at these two sites. By adjusting the P-wave velocity of the undisturbed samples in the laboratory so as to have the same velocity in the field, the in-situ state of saturation was reproduced in the laboratory samples. Then, the cyclic loading tests were conducted to determine the cyclic strength of intact samples. The results of the laboratory tests as above were incorporated into the simple method of liquefaction analysis described in the first section of this paper. The analysis seems to yield results which are in reasonably good agreement with what was observed at the time of the earthquake.     

An examination of the correlation between earthquake, positions of solar system bodies and solid tide

After processing 204 data of historical earthquakes for M ⩾ 4.5 from 1900 to 1996 in the area centered at Beijing (39.9°N, 116.4° E; ±3°), two correlations have been suggested: One is between earthquake and the position distribution of major solar system bodies; the other is between the earthquake magnitude and the tidal force at the epicenter. A tentative is presented for future seism prediction. Because this work is at the test stage based on a statistic analysis, further test and verification are expected.     

Earthquake曲线切向量上的范数

本文研究了定义在earthquake曲线切向量上的范数，首先证明了一条earthquake曲线ht上初始切向量的范数等价于earthquake测度σ的Thurston范数．其次证明了当t→∞时，ht的切向量Vt的范数增长渐近等于O(||→||The^Ct||σ||Th)，其中C是正的万有常数，||σ||Th是σ的Thurston范数，而O所代表的常数是渐近万有的，也即当t||σ||Th充分大时它是万有的．此外，附带证明了定义在Zygmund有界函数上的两种交比范数是等价的．     

THE PRECURSOR OF INSTABILITY FOR NONLINEAR SYSTEMS AND ITS APPLICATION TO EARTHQUAKE PREDICTION

By analysing the instability process of various nonlinear systems, we conclude that their instability precursors are the continual heightening of the response rate or response ratio.Applying this theory to earthquake prediction, we adopt the periodical change of the stress in crust caused by the tide-generating force as the loading and unloading. If we can measure the ratio of the response (such as crust deformation, gravity and seismicity) during the loading period to that during the unloading period, this parameter must contain some characteristic information about the seismogenic process.With nine earthquakes (M≥7) data that occurred in Chinese mainland during 1970-1988, we take the sum of square root o?energy of small earthquakes, which is called the released strain by Benioff, as the response to the tidal loading and unloading. We find that the response ratios of seven earthquakes increase obviously before the main earthquakes.     

New evidence of earthquake precursory phenomena in the 17 January 1995 Kobe earthquake, Japan

Significant advances, both in the theoretical understanding of rupture processes in heterogeneous media and in the methodology for characterizing critical behavior, allows us to reanalyze the evidence for criticality and especially log-periodicity in the previously reported chemical anomalies that preceded the Kobe earthquake. The ion (Cl^-, K⁺, Mg⁺⁺, NO₃ ^- and SO₄ ^-) concentrations of ground-water issued from deep wells located near the epicenter of the 1995 Kobe earthquake are taken as proxies for the cumulative damage preceding the earthquake. Using both a parametric and non-parametric analysis, the five data sets are compared extensively to synthetic time series. The null-hypothesis that the patterns documented on these times series result from noise decorating a simple power law is rejected with a very high confidence level. Received 21 January 2000     

Criticality features in ULF magnetic fields prior to the 2011 Tohoku earthquake

The criticality of ULF (Ultra-low-frequency) magnetic variations is investigated for the 2011 March 11 Tohoku earthquake (EQ) by natural time analysis. For this attempt, some ULF parameters were considered: (1) F_h (horizontal magnetic field), (2) F_z (vertical magnetic field), and (3) D_h (inverse of horizontal magnetic field). The first two parameters refer to the ULF radiation, while the last parameter refers to another ULF effect of ionospheric signature. Nighttime (L.T. = 3 am ± 2 hours) data at Kakioka (KAK) were used, and the power of each quantity at a particular frequency band of 0.03–0.05 Hz was averaged for nighttime hours. The analysis results indicate that F_h fulfilled all criticality conditions on March 3–5, 2011, and that the additional parameter, D_h reached also a criticality on March 6 or 7. In conclusion, criticality has reached in the pre-EQ fracture region a few days to one week before the main shock of the Tohoku EQ.