三水准超越概率水平地震动峰值加速度关系分析

以35个工程场地地震安全性评价结果为样本,统计分析了三水准超越概率水平地震动峰值加速度（PGA）关系。结果表明：50年超越概率63％和2％地震动峰值加速度与50年超越概率10％地震动峰值加速度的比值,在不同场地类别条件下变化不显著。     

2014年云南鲁甸6.5级地震强震动观测记录及初步分析

2014年8月3日云南鲁甸发生MS6.5地震,在震中及其周边地区分布的中国数字强震动台网的81个台站获取了这次地震的主震强震动记录.特别是位于极震区鲁甸龙头山镇财政所强震动台,完整记录到这次地震的地震动时程,其东西向PGA达948.5 cm/s2,该台站周边多栋多层建筑物底层完全倒塌和损毁,与记录所反映的强烈震动相吻合.初步分析强震动观测记录,讨论了本次地震的震中位置、破裂方向和强震动衰减速率等问题.     

谱强度SI和地震动峰值加速度PGA参数在高铁列车地震预警中的应用

为了降低没有破坏性的高频小震对高铁地震报警的干扰,引入谱强度SI参数作为报警参数,分析其在高铁地震报警中的适用性。研究发现低频振动对SI的影响比高频振动大,对于高铁线路附近的高频小震,SI参数能有效的排除,但对于破坏性不大的远震大震可能会引发报警,从而产生误报现象,影响高铁列车运行效率。为了降低SI在破坏性小的远震大震中的误报率,本文引入PGA与SI作为报警参数。最后给出了不同时速下基于PGA与SI联合报警的阈值供参考。     

医用CT增益可编程的多路高速数据采集系统设计

介绍了一种医用CT增益可编程的多路高速数据采集系统,该系统以FPGA为时序控制器,以ADC4344为模数转换器,通过串行移位寄存器控制多路模拟开关实现多路模拟数据的采集,并采用可编程增益放大器提高了系统的分辨率。该系统电路结构简单,对多路高速、宽动态范围的数据采集系统具有一定的通用性,可根据系统的需要进行扩展。     

Attenuation of peak ground accelerations from the great Wenchuan earthquake

Over 800 accelerograms recorded by 272 ground-level stations during the Wenchuan earthquake are used to analyze the influence of rupture distance, local site conditions and azimuth on peak ground accelerations (PGAs). To achieve a better understanding of the characteristics of ground motions, the spatial distributions of the EW, NS and UD components of PGAs arc obtained. Comparisons between the EW and NS components, the fault-normal and fault-parallel components,and the vertical and horizontal components of PGAs are performed, and the regression formula of the vertical-to-horizontal ratio of PGAs is developed. The attenuation relationship of peak horizontal accelerations (PHAs) is compared with several contemporary attenuation relationships. In addition, an analysis of residuals is conducted to identify the potential effects of rupture distance, azimuth and site conditions on the observed values of PHAs. The analysis focuses on medium-hard soil site conditions, as they provided most of the data used in this study.     

利用国家数字地震台网记录计算汶川地震余震峰值加速度分布图

数字地震台网可实时获取地震记录,因此可据此快速计算地震动参数,如峰值加速度、峰值速度的分布图,为震后救灾提供参考依据。本文对国家数字地震台网的地震记录,采用插值型求导公式中的两点公式计算加速度时程,并通过计算原始记录和仿真加速度时程的幅值谱,检验了结果的可靠性。最后对汶川大地震后的两个强余震进行了计算和分析,作出了峰值加速度分布图。     

Analysis of nonlinear site response using the LSST downhole accelerometer array data

Both linear and nonlinear behaviors of soil deposits were evaluated by strong and weak motion data observed on the surface and at depths of 6, 11, 17, 47 m at the Large Scale Seismic Test (LSST) array in Lotung, Taiwan. The soil properties measured by well logging and by the shear wave velocity profile measured by uphole and cross-hole methods are available. Both one-dimensional equivalent-linear method and nonlinear method are used for the evaluation have been used. The synthetic records at various depths are obtained by using the records at the bottom as input motion. These synthetic records are then compared with actual records at corresponding depths. Records of 13 earthquakes are used. We find that the synthetic records obtained from a linear model match well with actual records for small input motions, but the results obtained from a nonlinear model match poorly. On the other hand, the synthetic records using both the nonlinear model and equivalent-linear model are in good agreement with the observed records for large input motions. In these cases, the predicted response spectra using the linear model consistently overestimate the observed records. The threshold distinguishing the large and small input motions is 0.04 g at depth of 47 m for the LSST data. Thus, the nonlinearity started at 0.04 g and occurred unequivocally at 0.075 g. Furthermore, the dominant frequencies shift toward lower values when input motions become large. Clearly, the observed records at the LSST site manifest nonlinearity of soil response. The hysteresis loops evaluated by the nonlinear method show a permanent strain of about 0.01% in soil layers at higher ground motion input levels in this case.     

First Order Seismic Microzonation of Haldia, Bengal Basin (India) Using a GIS Platform

The seismic microzonation of the Bengal Basin, Haldia region, India is carried out using the Analytical Hierarchy Process (AHP) on the Geographic Information System (GIS). Three themes are used for the seismic microzonation, namely Peak Ground Acceleration (PGA), predominant frequency and elevation map. An analysis of the maximum magnitude (m _max) and the b value is carried out after preparing the earthquake catalogue from various sources. On the basis of the tectonic set up and seismicity of the region, five seismic zones are delineated which can be a threat to Haldia. They are broadly classified as Zone 1: Arakan-Yoma Zone (AYZ), Zone 2: Himalayan Zone (HZ), Zone 3: Shillong Plateau Zone (SPZ), Zone 4: Bay of Bengal Zone (BBZ) and Zone 5: Shield Zone (SZ). The m _max for Zones 1, 2, 3, 4 and 5 are 8.30 ± 0.51, 9.09 ± 0.58, 9.20 ± 0.51, 6.62 ± 0.43 and 6.61 ± 0.43, respectively. The PGA value is computed for Haldia following the attenuation relationship taking the m _max of each source zone. The expected PGA at Haldia varies from 0.09–0.19 g. The predominant frequency of Haldia is also calculated using the H/V ratio with a frequency ranging from 0.1–3.0 Hz. The elevation map of Haldia is also generated using the Shuttle Radar Topography Mission (STRM) data. A first-order seismic microzonation map of Haldia is prepared in which four zones of hazard have been broadly classified for Haldia as very high seismic hazard zone, high seismic hazard zone, moderate seismic hazard zone and less seismic hazard zone. The very high seismic hazard zone is observed along the southern part of Haldia where there are major industrial and port facilities. The PGA for the four hazard zones are: 0.09–0.13 g for low hazard zone, > 0.13–0.15 g for moderate hazard zone, > 0.15–0.16 g for high hazard zone and > 0.16–0.19 g for very high hazard zone.     

近断层竖向地震动峰值特征

为了研究近断层区域竖向地震动的加速度峰值衰减特征和竖向与水平加速度峰值比特征,为进行近断层区域结构抗震设计和地震危险性分析等提供基础数据参考,根据1952—1999年世界范围内震级在M5．4-M7．6之间的18次地震的地震动记录提出一种同时考虑断层距和震级影响的竖向峰值加速度衰减关系,并与其他学者提出的衰减关系进行了对比分析。然后初步统计分析了竖向与水平峰值加速度比值、竖向地震动PGV／PGA比值的特征。研究结果表明,本文提出的加速度峰值衰减关系形式比较简单而且能较好地体现地震动加速度峰值的衰减变化关系;断层距在0—40km范围内相当一部分竖向与水平向峰值加速度比值大于一般抗震设计规范中规定的比值即0．65;至少对于竖向地震动而言,只将PGV／PGA〉0．2s作为识别近断层脉冲型地震动的强度指标是不够的。     

Seismic hazard in mega city Kolkata, India

The damages caused by recent earthquakes in India have been a wake up call for people to take proper mitigation measures, especially the major cities that lie in the high seismic hazard zones. Kolkata City, with thick sediment deposit (∼12 km), one of the earliest cities of India, is an area of great concern as it lies over the Bengal Basin and lies at the boundary of the seismic zones III and IV of the zonation map of India. Kolkata has been affected by the 1897 Shillong earthquake, the 1906 Calcutta earthquake, and the 1964 Calcutta earthquake. An analysis on the maximum magnitude and b-value for Kolkata City region is carried out after the preparation of earthquake catalog from various sources. Based on the tectonic set-up and seismicity of the region, five seismic zones are delineated, which can pose a threat to Kolkata in the event of an earthquake. They are broadly classified as Zone 1: Arakan-Yoma Zone (AYZ), Zone 2: Himalayan Zone (HZ), Zone 3: Shillong Plateau Zone (SPZ), Zone 4: Bay of Bengal Zone (BBZ), and Zone 5: Shield Zone (SZ). The maximum magnitude (m _max) for Zones 1, 2, 3, 4, and 5 are 8.30 ± 0.51, 9.09 ± 0.58, 9.20 ± 0.51, 6.62 ± 0.43 and 6.61 ± 0.43, respectively. A probability of 10% exceedance value in 50 years is used for each zone. The probabilities of occurrences of earthquakes of different magnitudes for return periods of 50 and 100 years are computed for the five seismic zones. The Peak Ground Acceleration (PGA) obtained for Kolkata City varies from 0.34 to 0.10 g.