共查询到20条相似文献，搜索用时 15 毫秒
1.
分析G-R-闵公式后得出,它是从点源幅射场导出的,与地震宏观场不相应。因在近场震源不能视作点源。在分析过程中,导出相当于点源、线源或面源以及复杂源的幅射场的深度公式。对实际的地震,它的源类型一无所知,所以不预作假定,将源指标几何扩散率n作为待定参数,导出了一个物理意义明确而又普遍化的震源深度公式。此公式的诸解法中,以计算方法准确、精度高,作图法有直观的优点,但准确性差、精度低,图算法只作获取粗略值和考察数据均匀性用。计算了9个8级以上巨震、1个71/2大震,和两个M_L=3的有感地震的震源深度,经对比结果很好,利用计算得出震源类型,结合宏观场研究了这些地震的震源几何学。并且首次在国际上给出宏观地震震源深度值的标准误差。 相似文献
2.
作者根据位错模型导出了震级不仅与震中烈度和震源深度有关,而且与极震区面积有关。震中烈度通过应力降和震级联系起来,而极震区面积则通过位错面的面积或震源体积和震级联系起来,使震级与烈度的物理联系更加明确。 用我国的61个浅源地震资料,用逐步回归方法计算出震级M与震中烈度I0、极震区面积（面积单位为平方公里）A0的关系为: M=3.53+0.039I02+0.0178（Ig A0）3,还分别计算出震级与6-8度区面积A6、A7、A8的关系为: M=3.63+0.72 Ig A6, M=5.34+0.718（Ig A7）·（IgIg A7）, M=5.92+0.104（Ig A8）2。并外推出震级与5度区面积A5的关系为: M=3.03+0.72 Ig A5。 利用这些关系式来确定历史地震震级比仅考虑震中烈度来确定有较好的效果。 相似文献
3.
根据常用公式 h=Δi/10（I0-Ii）/s-11/2, 式中h为震源深度,Δi为烈度为Ii的等震綫半径,I0为震中烈度,S为一系数;取（1）式的对数得 logh=logΔi-1/2log[10（I0-Ii）/s-1], 按（2）式可以作成一量版,以同时測定h和s。利用这个量版測定了19个中国地震的s和h,結合文献[4]的資料,指出中国东部的s系数比西部的偏低;且当深度加大时,s系数加大。采用文献[1,5]的資料測定了61个地震的s系数,結果表明s的数值随深度的增加而加大,占与低速层的关系并不明显。 相似文献
4.
Marco Cattaneo Paolo Augliera Stefano Parolai Daniele Spallarossa 《Journal of Seismology》1999,3(4):421-435
It is usually assumed that earthquakes in intraplate regions occur in the upper crust, and northwestern Italy is generally assigned to this kind of normal seismicity. In this work, the depth distribution of the events localized in this area by the Istituto Geofisico Geodetico (IGG) seismic network in the period 1991–1997 is analyzed in detail. In particular, the location capability of the network is discussed, adopting as reference quarry blasts (for the epicentral position) and the locations obtained from a dense temporary network (for the depth estimate). Within the so-obtained error limits, the depth distribution of events show a characteristic pattern: while for most of the area covered by the network the well-located seismicity lies within the first 20 km of depth, in a band following the inner arc of the Western Alps, numerous events have anomalously large focal depths, reaching a maximum of 114 km. These depth determinations cannot be attributed to instabilities of the location procedure: different choices of the propagation models used for the hypocentral determination led to very similar depth values, always significantly larger than the standard values for the surrounding areas. A strong correlation has been found between the 3-dimensional distribution of these foci and the P-wave propagation anomalies obtained from tomographic studies, suggesting a direct link between elastic and rheological properties of lower crust and upper mantle in this area. 相似文献
5.
2003年云南大姚6.2级、6.1级地震中短期地震学异常演化特征 总被引：1，自引：0，他引：1
通过对2003年云南大姚6．2级、6．1级地震中短期地震学特征的分析和初步研究，认为大姚地震孕育过程中的短期阶段，震中附近的地震学异常以中小地震活动增强为主，表现为震区附近中小地震频度增加，4级震群活动、A值、GL值出现异常，同时震源深度加深等；在由中期向短期过渡的过程中，震源区异常消失相对平静，使多种地震学异常收缩至震源区附近；地震孕育进入短临阶段，震中附近地区再次出现了3～4级小震活动增强的特征，云南省地震活动出现向震中附近迁移的趋势。整个孕震过程，地震活动体现了活动-平静-活动的动态演化特征。 相似文献
6.
Geological and macroseismic effects of the Muya, 1957 earthquake and palaeoearthquakes in Baikal region 总被引：2，自引：0，他引：2
R. E. Tatevossian N. G. Mokrushina A. N. Ovsyuchenko T. N. Tatevossian 《Seismic Instruments》2010,46(2):152-176
Intensity of the Muya, 1957 earthquake is assessed in localities based on macroseismic data and in epicentral area based on
effects in natural environment; it is analyzed how these assessments correspond to each other and to instrumental location
of epicenter, hypocentral depth, and magnitude; it is evaluated, how seismodislocations of the Muya earthquake could serve
as control of palaeoseismostructure parameters in this region. Spatial distribution of macroseismic effect confirms relatively
deep source (20–22 km). Deep source agrees with anomalously short surface rupture length (not more than 25 km); only a part
of the source exposed on the surface. Comparison with length of palaeoseismostructures shows that it is a regional feature.
Epicentral intensity based on surface ruptures is assed X degrees in ESI2007 scale. Ignoring geological effects will underestimate
epicentral intensity up to two degrees. Source mechanism with three sub-sources is in agreement with segmentation of surface
ruptures. Sub-sources are of strike-slip type with small normal component; essential normal slip at surface is probably not
representative for the source and is due to accommodation of strike-slip movement along with a system of sub-parallel en echelon
ruptures under tension. 相似文献
7.
MohammadQaisar TarigMahmood 《地震研究》2001,24(3):272-278
使用Bungum和Huseby方法对地方地震台网的监控能力和可靠性进行了分析。用震源位置的标准计算机码重新定位地震事件。由频率震级分布导出50％，90％和100％的累积监控能力阀值，对这些阀值23年内记录资料的监控能力水平作了估测。分析表明，在台网内发生的地震事件的台网100％监控能力水平为ML=1.7，从台网内固定实时震源对台网震源解精度作了分析。地震事件在台网内发生时，震中误差低于4km。最后讨论了地方地震台网连续运行期间影响监控能力的因素。 相似文献
8.
M.Qaisar T.Mahmood S.A.Khan 《地震学报(英文版)》2003,16(1):59-66
The detectability and reliability analysis for the local seismic network is performed employing by Bungum and Husebye technique.The events were relocated using standard computer codes for hypocentral locations.The de-tectability levels are estimated from the twenty-five years of recorded data in terms of 50%,90%and 100% cumu-lative detectability threshokls,which were derived from frequency-magnitude distribution.From this analysis the 100%level of detectability of the network is ML=1.7 for events which occur within the network.The accuracy in hypocentral solutions of the network is investigated by considering the fixed real hypocenter within the network.The epicentral errors are found to be less than 4km then the events occur within the network.Finally.the prob-lems faced during continuous operation of the local network,which effects its detectability,are discussed. 相似文献
9.
利用Bungum和Husebye的方法，分析了地方地震台网的检测能力和可靠性．用标准的计算机定位程序重新测定了地震位置．根据25年的地震记录，分别由震级-频度关系导出的50%、90%和100%的累积检测率估计了检测水平．对台网内地震，相应于100%检测率的震级下限为ＭＬ＝1.7．用台网内固定的实际震源，研究了台网对震源位置的测定精度．对网内地震，震中测定误差小于4 km．最后讨论了台网连续工作时可能会遇到的影响检测能力的一些问题． 相似文献
10.
晋冀鲁豫交界地区震源位置及震源区速度结构的联合反演 总被引：1，自引：0，他引：1
利用邯郸数字台网记录到的2001—2008年间460次ML≥1.0地震的1861条P波到时数据, 采用震源位置和速度结构联合反演方法确定晋冀鲁豫交界地区(35.0°~38.0°N, 113.0°~116.0°E)地震的震源位置分布和该区域的速度结构。 结果表明: ① 经过重新定位后, P波走时的均方根残差(RMS)由反演前的1.35 s降到反演后的0.45 s。 定位偏差在EW方向上平均为0.031 km, 在NS方向上平均为0.029 km, 在垂直方向上平均为0.060 km。 ② 邢台震区的中小地震明显呈NEE向分布, 深度主要集中分布在7~14 km范围内; 磁县震区中小震分布相对复杂, 具有NEE和NWW两个展布方向, 震源深度主要集中在8~18 km范围内, 总体上晋冀鲁豫交界地区中小地震深度呈现北部浅南部深的趋势。 ③ 反演得到了晋冀鲁豫交界地区的速度结构, 在邢台地震极震区下方7~14 km处存在低速层, 与1966年邢台7.2级地震的震源深度一致;在磁县地震极震区下方13~18 km处也存在低速层与1831年磁县7.5级地震震源深度一致, 且磁县震区下方的速度结构比邢台震区更为复杂。 相似文献
11.
河西地区几次强震前的垂直地形变分维特征研究 总被引：1，自引：0，他引：1
采用关联维的计算方法,对河西地区门源6.4级和天祝一景泰6.2级地震过程中的垂直地形变序列的时、空分维数分别进行了计算,得到:本文研究区内远场(远离震中区)的地形变序列分维数在0.63～0.80之间,而近场(震中地区)的序列分维数在0.17～0.44之间,近场出现明显的降维现象;地震的孕、发过程中地形变观测序列分维数在0.22～0.37之间,而无震期间则在0.57～0.77之间,地震孕、发过程中地形变观测时间序列亦存在明显的降维现象。 相似文献
12.
Marian Ivan 《Journal of Seismology》2011,15(2):317-328
Crustal thickness (CT) in Vrancea region (Romania) and adjacent area is investigated using 1294 S to P converted waves from
the Moho discontinuity. A total of 269 local earthquakes in the depth range 99.8 to 171.1 km and recorded by 76 permanent
and 46 temporary stations of the Romanian Seismological Network are used. Time difference between the converted wave and the
direct P phase is corrected to a first order for epicentral distance and for the errors in focal depth, being finally inverted
to CT. Greatest values for the Moho depth are observed for stations located in the Carpathians molasse foredeep and smaller
values are observed in the Southern part of the Moesian Platform, for stations in the eastern part of Moldavian (East-European)
Platform and in Dobrogea area, close to the Black Sea shoreline. In Vrancea epicentral area, an important CT variation is
observed, from 42 km at MLR and 41.8 km at SIR, stations placed in the south-western part of the epicentral area, to 30.9 km
at VRI, located above north-eastern part of the seismogenic volume. Stations CVO and OZU, placed in Transylvanian Basin in
the proximity of the epicentral area, have CT values of 32.1 and 24.1 km, respectively. The results seem to support that a
mantle delamination process is responsible for Vrancea intermediate depth seismicity. 相似文献
13.
Calibration of the Regional Crustal Waveguide and the Retrieval of Source Parameters Using Waveform Modeling 总被引：5，自引：0，他引：5
v--vRegional crustal waveguide calibration is essential to the retrieval of source parameters and the location of smaller (M < 4.8) seismic events. This path calibration of regional seismic phases is strongly dependent on the accuracy of hypocentral locations of calibration (or master) events. This information can be difficult to obtain, especially for smaller events. Generally, explosion or quarry blast generated travel-time data with known locations and origin times are useful for developing the path calibration parameters, but in many regions such data sets are scanty or do not exist. We present a method which is useful for regional path calibration independent of such data, i.e. with earthquakes, which is applicable for events down to Mw = 4 and which has successfully been applied in India, central Asia, western Mediterranean, North Africa, Tibet and the former Soviet Union. These studies suggest that reliably determining depth is essential to establishing accurate epicentral location and origin time for events. We find that the error in source depth does not necessarily trade-off only with the origin time for events with poor azimuthal coverage, but with the horizontal location as well, thus resulting in poor epicentral locations. For example, hypocenters for some events in central Asia were found to move from their fixed-depth locations by about 20 km. Such errors in location and depth will propagate into path calibration parameters, particularly with respect to travel times. The modeling of teleseismic depth phases (pP, sP) yields accurate depths for earthquakes down to magnitude Mw = 4.7. This Mw threshold can be lowered to four if regional seismograms are used in conjunction with a calibrated velocity structure model to determine depth, with the relative amplitude of the Pnl waves to the surface waves and the interaction of regional sPmP and pPmP phases being good indicators of event depths. We also found that for deep events a seismic phase which follows an S-wave path to the surface and becomes critical, developing a head wave by S to P conversion is also indicative of depth. The detailed characteristic of this phase is controlled by the crustal waveguide. The key to calibrating regionalized crustal velocity structure is to determine depths for a set of master events by applying the above methods and then by modeling characteristic features that are recorded on the regional waveforms. The regionalization scheme can also incorporate mixed-path crustal waveguide models for cases in which seismic waves traverse two or more distinctly different crustal structures. We also demonstrate that once depths are established, we need only two-stations travel-time data to obtain reliable epicentral locations using a new adaptive grid-search technique which yields locations similar to those determined using travel-time data from local seismic networks with better azimuthal coverage. 相似文献
14.
Centroid Depth Versus Hypocentral Depth： Their Distribution and Depth／Mechanism Dependence 总被引：1，自引：0，他引：1
The Harvard Global CMT catalogue from 1977 to 1998 is analyzed to investigate the relation between the centroid depth and the hypocentral depth. It is observed that for shallow earthquakes, the hypocentral depth is systematically larger than the centroid depth, while for deep-focus earthquakes there is no statistically significant difference between the distributions of centroid and hypocentral depth. A detailed look at the result reveals that such a systematic difference is mainly from the contribution of thrust and normal earthquakes, while strike-slip earthquakes have no such regularity. It turns out that for shallow thrust and normal earthquakes, seismic rupture tends to initiate from the deeper part. 相似文献
15.
Deterministic earthquake damage and loss assessment for the city of Bucharest, Romania 总被引：1，自引：0，他引：1
Dominik Lang Sergio Molina-Palacios Conrad Lindholm Stefan Balan 《Journal of Seismology》2012,16(1):67-88
On March 4, 1977, an earthquake with a moment magnitude M
w 7.4 at a hypocentral depth of 94 km hit the Vrancea region (Romania). In Bucharest alone, the earthquake caused severe damage
to 33,000 buildings while 1,424 people were killed. Under the umbrella of the SAFER project, the city of Bucharest, being
one of the larger European cities at risk, was chosen as a test bed for the estimation of damage and connected losses in case
of a future large magnitude earthquake in the Vrancea area. For the conduct of these purely deterministic damage and loss
computations, the open-source software SELENA is applied. In order to represent a large event in the Vrancea region, a set
of deterministic scenarios were defined by combining ranges of focal parameters, i.e., magnitude, focal depth, and epicentral
location. Ground motion values are computed by consideration of different ground motion prediction equations that are believed
to represent earthquake attenuation effects in the region. Variations in damage and loss estimates are investigated through
considering different sets of building vulnerability curves (provided by HAZUS-MH and various European authors) to characterize
the damaging behavior of prevalent building typologies in the city of Bucharest. 相似文献
16.
17.
Shengzao Chen 《地震学报(英文版)》1992,5(4):749-758
Seismotectonic characteristics and its relationships with crustal structure have been analyzed in the lower Yangzi—South Yellow
Sea area. The finite element method is employed to evaluate the stress-strain status of the lithosphere, and the dynamic origin
of earthquakes is discussed. The moderate-weak earthquake division is tectonically controlled by three first-degree faults
in the Hangzhou bay—Qinling, Tancheng—Lujiang, and the Yangzi River mouth—Jizhou island. The earthquake frequency is higher
than 70% in the major hypocentral layer of the crust at a depth of 5 to 15 km of which the highest frequency particularly
emerges at a depth of 10 to 15 km, and generally, the depth ranges from 5 to 20 km in the predominant hypocentral layer. The
hypocentral layer is superimposed in the crustal magnetosphere with the mid-crustal low density layer. The results from the
finite element analysis show that the maximum horizontal displacements appear in the hypocentral layer of the crust, and that
the radial hypocentral zones on the flanks of the anomalous mantle, accompanied by the faults or fractured zones, correspond
to the gradient zones of the major principal stresses and strains varying within the lithosphere. Therefore, we could consider
the mechanism of the decoupling-drift of the lithosphere and the crustal sliding or detachment, from the continent to the
sea, as a main dynamogenesis of the earthquakes in the area studied.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, 164–171, 1992.
This research was supported by the China National Post-Doctoral Research Foundation in part. Some contents on the aeromagnetic
anomalies and their mathematical processes are deleted in revision. 相似文献
18.
E. A. Rogozhin 《Izvestiya Physics of the Solid Earth》2013,49(5):643-652
The seismotectonic, seismological, macroseismic, and geodetic investigations carried out by different authors provided the idea about the size and structure of the sources of the largest Simushir earthquakes that occurred on November 15, 2006 and January 13, 2007. Sound conclusions concerning the character of dislocations arising in the epicentral area of strong submarine seismic events are drawn from the detailed analysis of GPS-based geodetic observations of surface deformations on the islands and in the southern Kamchatka. The focal mechanism solutions for two of the strongest quakes, together with the hypocentral positions of their aftershocks, are used for identifying the fault plane and reconstructing the pattern of the slip on it. 相似文献
19.
段星北 《地震学报(英文版)》1997,10(6):731-741
ＧｅｏｇｒａｐｈｉｃａｌｄｉｓｔｒｉｂｕｔｉｏｎｏｆｈｙｐｏｃｅｎｔｒａｌｄｅｐｔｈｓｏｆＣｈｉｎｅｓｅｅａｒｔｈｑｕａｋｅｓＸＩＮＧ－ＢＥＩＤＵＡＮ（段星北）ＩｎｓｔｉｔｕｔｅｏｆＧｅｏｐｈｙｓｉｃａｌ，ＳｔａｔｅＳｅｉｓｍｏｌｏｇｉｃａｌＢｕｒ... 相似文献
20.
The caustic of SKP is found at an epicentral distance ΔC = 129.5° for surface foci and at ΔC = 128.9° for foci at 400 km depth, by means of amplitude-distance graphs based upon short-period time-domain measurements. These results are essentially confirmed by long-period time-domain measurements of SKP as well as by frequency-domain studies, even though the spectra are less accurate for such determinations. The average period of SKP is from short-period records, significantly different from the corresponding PKP-period of 1.00 ± 0.31 sec. Likewise, the long-period averages of SKP = 10.8 ± 4.5 sec and of PKP = 7.7 ± 3.0 sec are significantly different from each other. A travel-time table of SKP1 is deduced, covering the epicentral distance range of 130–143° and the focal depth range of 100–700 km. All results are based on measurements on seismograms of the Swedish network of stations, deriving almost exclusively from earthquakes in the southwest Pacific area. 相似文献