云南丽江峡谷的场地放大

分析S波土层/基岩和脉动水平/垂直的频谱比,分别得出了位于丽江峡谷南段、中段和北段的丽宾、白沙和玉龙3个台站的场地放大．使用的资料是1996年2月3日云南丽江MS＝7.0地震余震的数字记录．在1～4 Hz频率范围内,丽宾台S波东西分量土层/基岩频谱比最大,达4.5;丽宾台脉动土层北南/垂直频谱比接近1,东西/垂直频谱比约为4.5,且与上述土层/基岩频谱比相同．表明脉动的垂直和北南分量未被土层放大,单台Nakamura法可用．用此法进而求出了白沙和玉龙的脉动频谱比,它们具有同丽宾脉动频谱比类似的特征．在上述频率范围内,两台的北南/垂直频谱比接近1,而东西/垂直频谱比白沙台约为6,玉龙台约为4.5．在丽江峡谷有横越峡谷的方向性场地响应特征．     

昆明地震动强度(烈度)观测台场地动力特征研究

使用单点地脉动谱比法（Nakamura方法）,对3个昆明地震动强度（烈度）观测台的基墩和场地自由表面进行了谱比分析,通过分析谱比的卓越周期和放大因子,研究了基墩对地震波的影响和Nakamura方法对地层分析的可靠性。结果表明：（1）基墩对低频部分基本没有影响,对高频部分稍微有放大;（2）Nakamura方法对地层的分析和钻孔法所得的结果在某些层位较一致。     

1996年云南丽江7.0级地震人员死亡的社会学特征

笔者在丽江市古城区地震局查阅到1份丽江7.0级地震人员死亡的统计表,表中详细记录了死亡人员的年龄、性别、文化程度、职业、死亡原因、死亡地点等情况.通过对上述资料的分析,可得出本次地震死亡人员的年龄、性别、文化、职业特征.同时与国内同类研究相比,丽江地震造成的人员死亡具有普遍的一般特征,也具有云南民族地区、经济欠发达地区...     

地震放大效应与地下地质结构——龙门山山前玉皇观区域观测数据分析

通过布置于龙门山断裂带中段、龙门山山前玉皇观区域的地震观测台站阵列接收地震数据,研究该区域的地震动放大效应和地下地质结构.观测阵列共10台宽频带地震仪,分布在玉皇观河口冲积扇区域.分别采用参考场址谱比法（RSSR）和HV谱比法（HVSR）计算64个高信噪比近震数据的振幅谱比函数,结果显示在玉皇观区域具有较明显的地震动放大效应,并且局部场址效应显著.以S06场址为例,建立近地表地震地质模型,通过SH波放大效应正演模拟研究该场址的地震动放大模式.RSSR与HVSR的结果表明,两者所计算的场址放大效应主频一致,但是HVSR的放大峰值却比RSSR的放大峰值大一倍左右,表明HVSR的结果可能包含了波场在近地表低速层之下传播路径的改造作用.另外,采用27个远震P波的接收函数计算了该区域地壳上地幔S波速度结构.接收函数研究结果显示玉皇观地区的莫霍面深度为44 km,沉积盖层、结晶地壳和上地幔的S波速度分别为2.5 km·s^-1、3.5 km·s^-1和4.5 km·s^-1.观测阵列台站之间的接收函数反演结果一致性较好,说明本研究区域范围内地形地貌等近地表结构因素的相对变化对接收函数的影响不大.

     

1996年云南丽江7.0级地震人员死亡的社会学特征

A statistics analysis was conducted on the basic information about fatalities from the Lijiang MS7.0 earthquake in 1996. The factors include age, gender, educational background, occupation, cause of death, death place, etc. We found that even though deaths caused by the Lijiang earthquake had some common features with those from earthquakes in other places in China, it also showed some specific features because of the multiracial and economically-underdeveloped situation of Lijiang area. The results reached in the paper can serve as a reference for studying the features of casualties caused by future strong earthquakes in Yunnan, and for the delicate and human-oriented emergency treatment.     

Seismotectonic environment of occurring the February 3, 1996 Lijiang M=7.0 earthquake, Yunnan Province

Lijiang-Daju fault, the seismogenic fault of the 1996 Lijiang M=7.0 earthquake, can be divided into Lijiang-Yuhu segment in the south and Yuhu-Daju segment in the north. The two segments show clear difference in geological tectonics, but have the similar dynamic features. Both normal dip-slip and sinistral strike-slip coexist on the fault plane. This kind of movement started at the beginning of the Quaternary (2.4～2.5 Ma B.P.). As to the tectonic types, the detachment fault with low angle was developed in the Early Pleistocene and the normal fault with high angle only after the Mid-Pleistocene (0.8 Ma B.P.). Based on the horizontal displacements of gullies and the vertical variance of planation surfaces cross the Lijiang-Daju fault at east piedmont of Yulong-Haba range, the average horizontal and vertical slip rates are calculated. They are 0.84 mm/a and 0.70 mm/a since the Quaternary and 1.56 mm/a and 1.69 mm/a since the Mid-Pleistocene. The movements of the nearly N-S-trending Lijiang-Daju fault are controlled not only by the regional stress field, but also by the variant movement between the Yulong-Haba range and Lijiang basin. The two kinds of dynamic processes form the characteristics of seismotectonic environment of occurring the 1996 Lijiang earthquake.     

Seismotectonic environment of occurring the February 3, 1996 Lijiang M=7.0 earthquake, Yunnan Province

Introduction The surface rupture and aftershocks of the February 3, 1996 Lijiang earthquake are basically distributed along the N-S-trending Lijiang-Daju fault, which is boundary fault between Lijiang Quaternary, fault controlled basin and Yulong-Haba range (ZHANG, et al, 1997). Corresponding to the surface geological features, the focal rupture of the Lijiang earthquake also shows large component of dip-slip. It is of great difference from that of other earthquakes in west Yunnan, in w…     

A hybrid approach for deriving horizontal site amplification factors considering both the similarity of HVSRE and the vertical amplification correction function

Under hypothetical and idealized conditions, the horizontal site amplification factor (HSAF) is defined as the ratio of the horizontal Fourier amplitude spectrum (FAS) at a point on the Earth's surface with respect to the horizontal FAS at the identical location but on the outcropping seismological bedrock. The HSAF reflects the profile of local sedimentary soils and weathered rock formations, indicating site effects. In most cases, such an idealized HSAF is difficult to measure directly. Thus, quantitatively estimating a HSAF value is a crucial task in strong-motion prediction over the last century. Fortunately, many strong-motion stations have been constructed throughout Japan, facilitating the characterization of HSAFs down to seismological bedrock at more than 1600 observational sites by the generalized inversion technique (GIT). First, this study reported the similarity distribution of the HSAF and the horizontal-to-vertical spectral ratio of earthquakes (HVSR_E). Subsequently, we proposed a hybrid method from a novel aspect for estimating HSAF in terms of the observed similarity distribution and the vertical amplification correction function (VACF) proposed previously. Compared with the direct use of HVSR_E for substituting HSAF, the hybrid method proposed herein demonstrated an improvement of greater than 30% in terms of the residuals between estimated HSAFs and those separated from observations.     

云南永胜期纳盆地的场地放大

根据2001年云南永胜Ms6．0地震的57个余震的304条数字地震记录,用线性反演法得出了期纳盆地相对于三道河台频率1．5～20Hz的S波场地放大。有实际放大作用的频率在10Hz以下,期纳台、半屏台和黄泥田台的放大峰值在4．5Hz处,糖厂台和龙门村台的放大峰值在7．5Hz处。所有台的峰值都约为三道河台的两倍。用永胜(基岩)区域数字地震台的记录作参考核算,10Hz以下,三道河台的场地放大约为1,其余台约为2,所以三道河台可作为基岩台看待。     

Site Response from Ambient Vibrations in the Towns of Lod and Ramle (Israel) and Earthquake Hazard Assessment

Throughout their long history, the towns of Lod and Ramle have been severely affected by strong earthquakes. The last destructive earthquake occurred on July 11, 1927 and caused the destruction of large parts of these cities, reaching a seismic intensity of VIII–IX on the MSK scale. Such a high intensity from a relatively distant earthquake (about 70 km) of magnitude 6.2 is likely to be the result of local site effects of the sedimentary layers that may have significantly enhanced earthquake ground motions. This study is focused on estimating the seismic hazard to Lod and Ramle by implementing a three-step process (1) detailed mapping of the characteristics of the H/V spectral ratios from ambient noise, (2) incorporating geological information and well data to construct subsurface models for different sites within the investigated area and (3) estimating the seismic hazard in terms of uniform hazard site-specific accelerations. The horizontal-to-vertical spectral ratios of ambient noise were used to approximate the fundamental resonance frequencies of the subsurface and their associated amplitudes. About 360 sites in Lod and Ramle were instrumented for varying periods. The soil sites exhibits H/V peak amplitudes ranging from 4 to 6 in the frequency range 0.5–2.5 Hz. These data were used to constrain 1-D subsurface models that were developed using geological data and borehole information. H/V spectral ratio observations were checked against theoretical subsurface transfer functions at locations where borehole information is available farther constraint the range of possible V_s velocities of the different layers and thus, by means of trial an error it was possible to conclude a systematic spatial distribution of the V_s velocity and thickness in the substrata that are also consistent with the spatial distribution of the fundamental resonance frequencies of the soft sediments obtained by means of the H/V spectral ratios, and other geological and geophysical information available at different locations in the study area. The evaluated subsurface models are introduced using the SEEH procedure of Shapira and van~Eck [(1993) Natural Hazards 8, 201–205] to assess Uniform Hazard Site-Specific Acceleration Spectra for different zones within the towns of Lod and Ramle. These evaluations are very important for realistic assessment of the vulnerabilities of all types of existing and newly designed structures and for urban and land use planning.     

Site Effect and its Relationship to the Intensity and Damage Observed in the June 27, 1998 Adana-Ceyhan Earthquake

The site response at 15 stations in the Adana-Ceyhan region (Southern Turkey) is calculated from the recordings of aftershocks of June 27, 1998 Adana-Ceyhan earthquake (M_S=6.2) by using the Standard Spectral Ratio (SSR) and the Horizontal-to-Vertical Spectral Ratio (HVSR) methods. While the two methods are in good harmony at a few stations in determining the site effects, they show differences on the estimated amplifications or on the site resonance frequencies at most stations. It was not clear which one of the two methods underestimates or overestimates the amplification values. We observe that at some stations, where the local site conditions are rather complex, the vertical component records are strongly influenced from the local soil conditions. Thus, the HVSR method fails at these stations. The SSR method underestimates the amplifications at some stations since the rock site, selected as reference site, has its own site response and/or the path correction we applied, considering the geometrical spreading factor only, is insufficient. At the sites where high intensity values were observed, we found high amplifications. The fundamental soil frequencies characterize the damage properties observed in the Adana-Ceyhan earthquake. The fundamental soil frequency is nearly at 1.1 Hz at the Ceyhan site, where severe damage was observed in the 5–6 story buildings, while the fundamental soil frequency is between 3–6 Hz at the Adana site, where damage was in the low-story buildings. Therefore, in addition to inefficient construction practices, it is clear that the resonance effects have also contributed to the observed damage.     

用H/V谱比法计算云南区域数字地震台站的场地响应

用H/V谱比法,计算给出了云南区域数字地震台网23个子台S波随频率变化的台站场地响应特征。结果表明:在1～10Hz频段内,23个子台S波的场地响应相对较平坦,在1.41～2.91之间变化,平均2.08;在大于10Hz的高频段,部分台站的场地响应有较明显的放大。     

岷县漳县6.6级地震黄土场地放大效应地脉动测试研究

2013年7月22日甘肃岷县漳县MS6.6级地震在极震区出现了黄土场地放大效应,为了从理论上解释黄土场地放大效应的原理,本文利用地脉动测试了极震区2个典型的黄土场地进行研究。结果发现:在黄土覆盖地区场地卓越频率特征显著,即在同一区域内山顶卓越频率较低,集中在1～2Hz,山沟卓越频率较高,集中在3～6Hz;同时,黄土场地随着高程的增加表现为厚黄土分布特征,其场地卓越频率在1.3～1.8Hz,与地震观测波的卓越频率1.0Hz接近,呈现出较明显的场地放大效应。结果与实际受灾情况相符。     

ESTIMATION OF SITE AMPLIFICATION FROM DAHAN DOWNHOLE RECORDINGS

Four-level Dahan downhole recordings are used to investigate site amplification due to the near-surface structure. The downhole array is installed at the depths of 0 m (surface), 50, 100 and 200 m. Eight sets of data presenting well-separated incident and reflected waves (from the free surface) are selected to analyse the site amplification. Five techniques of spectral ratios have been tested to determine the most reliable way to estimate site response. The superior one is the ratio of Root-Mean-Square (RMS) Fourier amplitude spectra, because it has the minimum number of pseudopeaks. However, the pseudopeaks can be further reduced by omitting those ratios with small denominators. Results show that the amplification factors are nearly uniform at the depths of 50 and 100 m, where their values fall between one and two. This factor is frequency-dependent at the surface and in the range from two to five under 6 Hz. These results agree well with those from time-domain analyses and the transmission-coefficient estimation except that the latter overestimates the amplification factor of the surface station. This suggests that the shallow velocity structure provided by the geotechnical survey might be underestimated. Numerical modelling also supports the underestimation of velocity at near surface since the synthetic SH waves based on a modified velocity model can match these observations well.     

Preliminary estimation for the focal mechanisms of 1996 Lijiang main shock in Yunnan Province and studies of related problems

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Characteristics of the Variation of Cross Fault Short-Baseline and Short-Range Leveling in Western Yunnan Earthquake Test Site Before Lijiang M_S7.0 Earthquake

Results of analysis of variation of cross fault short-baseline and short-range leveling in Western Yunnan Earthquake Test Site (WYETS), results show that among five observation stations of cross fault short-baseline and short-range leveling in WYETS before the Lijiang MS7.0 Earthquake occurred in February 1996 only Yongsheng observation station (epicentral distance 82 km) located at Chenghai fault shows great variation about one year before the earthquake. And the nearest observation station, Lijiang (epicentral distance 42 km); presents great coseismic variation, but does not show obvious anomalous variation before the earthquake. There are no significant variations related to the earthquake at the other three observation stations. Two methods are used in analysis of the observed data and some valuable results have been obtained.     

Body waveform inversion for the source process of the February 3, 1996 Lijiang, Yunnan earthquake

The source process of February 3, 1996 Lijiang earthquake in Yunnan was studied by body waveform inversion using teleseismic data from IRIS. Two normal double-couple subevents with different strikes were obtained. The difference of the onset time between these two subevents, which are 15 km apart in space, is 7 s. The total seismic moment is 3.81 × 10¹⁸ Nm (M _w=6.3). The total fault area S is about 720 km² from the aftershock data and the average dislocation is about ū=0.18 m. Considering both the result of inversion and tectonic environment around the source, the first rupture might result from the extension along the NNW directed Zhongdian-Yongsheng fault belt where an earthquake of M=6.4 occurred in 1966. Then, the second started along the NE directed the eastern foot of Snow Mountain fault where rupture seemed to be able to propagate more easily.     

Site amplification in lava rock on soft sediments

Seismicity and volcanic activity in Iceland are related to the Mid-Atlantic plate boundary that crosses the island. Due to volcanic activity, different sea levels through the ages and glacial drift, the geology in Iceland is quite complex at many sites. In June 2000, two major earthquakes of magnitude 6.6 (M_w) and 6.5 (M_w) occurred in southern Iceland. Ground motion from these main shocks and a number of aftershocks were recorded at the Icelandic strong motion network operated by the University of Iceland. At one of the instrumented sites considerable amplification was recorded on lava-rock overlying alluvial deposits. This site fits poorly in the soil classification systems of most earthquake codes. In this paper the recorded data is analyzed with different methods and the results are compared with the results of a one-dimensional site response analysis. The different methods produce the same characteristic of soil amplification at the site. The findings of this study have important implications for design criteria for sites with similar geology.     

禄丰武定丽江诸地震的相互关系--兼论丽江地震的预报

采用h′值和h值研究了禄丰、武定、丽江诸地震，指出了它们相互依存的关系。最后着重研究了丽江地震的预报，为今后地震预报积累了经验。     

A study of local amplification effect of soil layers on ground motion in the Kathmandu Valley using microtremor analysis

Past researchers have anticipated the occurrence of a great earthquake in the central Himalayas in the near future.This may cause serious damage in the Kathmandu Valley,which sits on an ancient lake be...