Relocation of aftershocks, focal mechanisms and stress inversion: Implications toward the seismo-tectonics of the causative fault zone of Mw7.6 2001 Bhuj earthquake (India)

The HYPODD relocation of 1172 aftershocks, recorded on 8–17 three-component digital seismographs, delineate a distinct south dipping E–W trending aftershock zone extending up to 35 km depth, which involves a crustal volume of 40 km × 60 km × 35 km. The relocated focal depths delineate the presence of three fault segments and variation in the brittle–ductile transition depths amongst the individual faults as the earthquake foci in the both western and eastern ends are confined up to 28 km depth whilst in the central aftershock zone they are limited up to 35 km depth. The FPFIT focal mechanism solutions of 444 aftershocks (using 8–12 first motions) suggest that the focal mechanisms ranged between pure reverse and pure strike slip except some pure dip slip solutions. Stress inversion performed using the P and T axes of the selected focal mechanisms reveals an N181°E oriented maximum principal stress with a very shallow dip (= 14°). The stress inversions of different depth bins of the P and T axes of selected aftershocks suggest a heterogeneous stress regime at 0–30 km depth range with a dominant consistent N–S orientation of the P-axes over the aftershock zone, which could be attributed to the existence of varied nature and orientation of fractures and faults as revealed by the relocated aftershocks.     

The Role of Residential Location in Conditioning the Effect of Metropolitan Economic Structure on Male Youth Employment

Youths have increasingly experienced labor market problems over the last several decades. One fruitful line of explanation focuses on structural changes in the demand for labor stemming from deindustrialization, changing skill requirements for employees, and increasing supply competition from women and recent immigrants. While these explanations merit attention, they have not adequately considered facts that condition their impact. This paper considers the argument that intra-metropolitan residential location conditions the effects of metropolitan labor market structure on black and white male youths' employment probabilities. Using a sample of individual-level data drawn from the 1990 census combined with metropolitan-level indicators of economic structure, it was found that some structural effects varied between central-city and suburban male youths. The conditioning role of residential location, and the subsequent nature of the structural effects, varied considerably between black and white male youths. Interpretations of the conditioning role of residential location include a variety of social and institutional effects on individual residents and the stigmatizing effects of some neighborhoods, especially on black male youths.     

面向自动车辆定位与导航系统的数字地图数据库系统

讨论了生成AVLN数字地图及相应数据库所必须采集的信息。重点分析了AVLN系统中几个依赖数字地图的功能。     

中国地震速报台网走时残差分析与走时修正

使用了３０个速报台站的观测数据,计算了１００多个中国境内外的地震事件初至波走时残差。在此基础上分析各台所记录的所有地震事件的残差随方位角和震中距的分布,及产生这些残差的地球深部非流体静力平衡状态和地球表面构造等方面的原因,并给出了不同区域地震走时的平均校正值,从而提高了地震定位精度。     

Relocation of shallow earthquakes in southern Alaska using Joint Hypocenter Determination method

A subset of 2660 shallow earthquakes (0–50 km) that occurred from 1988 to 1996 in south central Alaska between 155°W and 145°W and 59°N and 63°N was relocated using the joint hypocenter determination (JHD) method. Both P- and S-wave observations recorded by the regional seismic network were used. Events were relocated in twenty different groups based on their geographic location and depth using two velocity models. As a result of the relocation, the majority of the hypocenters shifted downward, while the epicenter locations did not change significantly. The distribution of the shallow subduction zone earthquakes indicates the existence of two seismically independent blocks, with one block occupying the northeastern part and the other occupying the central and western parts of the study area. The boundary between the blocks is marked by a 15 to 20 km wide seismicity gap to the southeast of 149.5°W and 62°N. The analysis of the fault plane solutions for shallow subduction zone earthquakes shows that an overwhelming majority of the solutions represent normal, oblique-normal or strike-slip faulting with predominant WNW-ESE orientation of T-axes. This indicates a down-dip extensional regime for the subducting slab at shallow depths. Very few earthquakes yielded fault plane solutions consistent with thrusting on a contact zone between the overriding and subducting plates. This result may be an indication that currently either the strain energy is not released at the contact zone or it is associated with aseismic motion.     

直接寻找油气田的土壤综合物性勘探方法技术

主要论述了用于直接寻找油气田的土壤综合物性勘探的机理和方法技术,包括土壤磁性（磁化率、天然剩磁、原生剩磁）、电性（电导率、氧化还原电位）、放射性等综合参数的利用。该方法成本低廉、野外施工简单、快捷,物性参数可在野外和实验室测定,属无源和非破坏性的勘探技术,为直接寻找油气田提供了一种新的思路和新的方法技术。     

An algorithm for the optimum distribution of a regional seismic network — II. An analysis of the accuracy of location of local earthquakes depending on the number of seismic stations

Summary Seven optimal networks consisting of 4 to 10 stations are compared for a given region, where velocity-depth profiles and the distribution of seismic intensity are known. Assuming that the standard error of arrival time is _t =0.05 s and the standard errors of the parameters of velocity-depth profiles are equal to 5% of their values, the average standard errors of the origin time and focus coordinates are estimated. The application of optimum methods to the planning of seismic networks in the Lublin Coal Basin is presented, and maps of standard errors of origin time , depth and epicenter ( _xy ) for the case of an optimum network of 6 seismic stations are given.     

INTERSTATE HIGHWAY EXIT MORPHOLOGY: NON-METROPOLITAN EXIT COMMERCE ON 1-75*

The commercial non-metropolitan exit clusters of America's interstate highway system exhibit regularities of basic form, scale, mix of services provided, and the ordinal placement of establishments relative to the exit proper. An examination of 354 exits serving 1-75 indicates the typical morphology of interstate exit clusters.     

基于iBeacon的精细室内定位方法研究

苹果公司发布的i Beacon作为一种粗精度位置感知服务体系,得到了广泛关注。针对更精细的广域位置服务,提出了基于i Beacon的无线指纹定位方法,并给出了图书馆的位置服务示例。