Probabilistic seismic hazard zonation of Syria     

Abdallah I. Husein Malkawi  Robert Y. Liang  Jamal H. Nusairat  Azm S. Al-Homoud 《Natural Hazards》1995,12(2):139-151

Earthquake hazard maps for Syria are presented in this paper. The Peak Ground Acceleration (PGA) and the Modified Mercalli Intensity (MMI) on bedrock, both with 90% probability of not being exceeded during a life time of 50, 100 and 200 years, respectively are developed. The probabilistic PGA and MMI values are evaluated assuming linear sources (faults) as potential sources of future earthquakes. A new attenuation relationship for this region is developed. Ten distinctive faults of potential earthquakes are identified in and around Syria. The pertinent parameters of each fault, such as theb-parameter in the Gutenberg-Richter formula, the annual rate ₄ and the upper bound magnitudem ₁ are determined from two sets of seismic data: the historical earthquakes and the instrumentally recorded earthquake data (AD 1900–1992). The seismic hazard maps developed are intended for preliminary analysis of new designs and seismic check of existing civil engineering structures.  相似文献   

On some problems of seismic crustal phase     

葛焕称 《地震学报(英文版)》1995,8(1):57-63

ＯｎｓｏｍｅｐｒｏｂｌｅｍｓｏｆｓｅｉｓｍｉｃｃｒｕｓｔａｌｐｈａｓｅＨｕａｎ－ＣｈｅｎｇＧＥ（葛焕称）（ＳｅｉｓｍｏｌｏｇｉｃａｌＢｕｒｅａｕｏｆＪｉａｎｇｓｕＰｒｏｖｉｎｃｅ,Ｎａｎｊｉｎｇ２１００１４,Ｃｈｉｎａ）Ａｂｓｔｒａｃｔ：Ｉｎｔｈｉｓ...  相似文献   

微震仪有线传输避雷研究     

陈仲范  耿大伏 《华北地震科学》1995,13(4):70-74

本文通过对雷电放电分析,研究解决微震仪有线传输的避雷问题,并介绍接收雷电信号控制传输线上电荷对地短路的“ＤＢＬ－１”避雷仪。  相似文献   

合肥遥测台网地震速报系统     

刘东旺  黎捷 《地震地磁观测与研究》1995,16(6):27-34

论述了适用于遥测地震台网大震速报的一套计算机处理系统,系统设计以《全国遥测台网观测技术规范》和《近震分析》理论为依据,实现了数据输入,震相选择,数据处理,地震定位,震级计算,结果输出及贮存等多项功能,达到了快速确定地震三要素,提高速报速度和精度之目的,是一个较完善的,实用的速报系统。  相似文献   

Comparison of two methods for seismic hazard assessment in a low-seismicity area     

Th. De Crook  J. J. Egozcue 《Natural Hazards》1992,6(1):39-49

The EGO method, developed by Egozcue et al. and the SRAMSC method, originally developed by Cornell and later programmed by McGuire, to assess the seismic hazard, are compared for the low seismicity area Belgium, The Netherlands, and NW Germany. Using the same input data, the results of the EGO method without the majority criterion and the SRAMSC method with upper bound XII agree very well. The influence of the zoning is investigated for the EGO method. It is not necessary to define the zones for the EGO method so strictly as for the SRAMSC method, but too wide zones can give bad results.  相似文献   

综合利用地震多参数预测油气藏     

杨丙中  邓俊国 《吉林大学学报(地球科学版)》1990,(3)

以吉林省境内红星构造带(已发现油田)和杨柳青构造带(未发现油田)为试验区,首先利用地震地层学方法,研究间接参数特征,确定有利相带和有效圈闭,并在有效圈闭上选择了39个2×2cm时窗。在时窗内提取与地震波动力学有关的信息,即频率、振幅、频谱能量等,然后对这种信息进行统计计算,获得振幅方差等九个参数并对其进行综合分析,从已知油气藏出发,对未知圈闭油气状况进行了三级预测,指出了最有利的勘探靶区。  相似文献   

High-resolution shallow seismic identification of gas escape features in the sediments of Loch Tay, Scotland: tectonic and microbiological associations     

ROBERT W. DUCK  RODNEY A. HERBERT† 《Sedimentology》2006,53(3):481-493

High-resolution seismic reflection profiles (3·5 kHz) have revealed the presence of extensive interstitial gas accumulation within the sedimentary sequences of Loch Tay, Scotland, as identified by acoustic turbidity masking the seismic stratigraphy. Within the central section of the loch, in the deepest water area directly above the zone of the seismically active Loch Tay Fault, focused flows of gas through the sediment pile to the loch bed via chimneys and pockmarks, together with gas seeps within the water column, have been identified. Microbiological observations indicate that the gas is biogenic CH₄, produced by both chemoautotrophic (which use CO₂ as a source of carbon and H₂ as a source of energy) and aceticlastic species (which use acetate as a source of carbon and energy) of methanogens in the fine-grained, organic rich deposits that have been focused into the zone of accumulation in the deep central part of the loch. The spatial distribution of the gas escape features suggests that earthquake movements along the Loch Tay Fault are responsible for facilitating focused gas escape in this part of the loch, by the creation of new pathways and conduits through the sediment pile, along which gas can migrate upwards and exit into the water column. Relict pockmarks and associated chimneys identified in the seismic records indicate that gas escape has been taking place since Pleistocene times though the precise timings cannot be ascertained. This is the first time that such features have been reported from a lake in the UK.  相似文献   

Seismic potential of Southern Italy   总被引：1，自引：2，他引：1  

S. Jenny  S. Goes  D. Giardini  H.-G. Kahle 《Tectonophysics》2006,415(1-4):81-101

To improve estimates of the long-term average seismic potential of the slowly straining South Central Mediterranean plate boundary zone, we integrate constraints on tectonic style and deformation rates from geodetic and geologic data with the traditional constraints from seismicity catalogs. We express seismic potential (long-term average earthquake recurrence rates as a function of magnitude) in the form of truncated Gutenberg–Richter distributions for seven seismotectonic source zones. Seismic coupling seems to be large or even complete in most zones. An exception is the southern Tyrrhenian thrust zone, where most of the African–European convergence is accommodated. Here aseismic deformation is estimated to range from at least 25% along the western part to almost 100% aseismic slip around the Aeolian Islands. Even so, seismic potential of this zone has previously been significantly underestimated, due to the low levels of recorded past seismicity. By contrast, the series of 19 M6–7 earthquakes that hit Calabria in the 18th and 19th century released tectonic strain rates accumulated over time spans up to several times the catalog duration, and seismic potential is revised downward. The southern Tyrrhenian thrust zone and the extensional Calabrian faults, as well as the northeastern Sicilian transtensional zone between them (which includes the Messina Straits, where a destructive M7 event occurred in 1908), all have a similar seismic potential with minimum recurrence times of M ≥ 6.5 of 150–220 years. This potential is lower than that of the Southern Apennines (M ≥ 6.5 recurring every 60 to 140 years), but higher than that of southeastern Sicily (minimum M ≥ 6.5 recurrence times of 400 years). The high seismicity levels recorded in southeastern Sicily indicate some clustering and are most compatible with a tectonic scenario where the Ionian deforms internally, and motions at the Calabrian Trench are small. The estimated seismic potential for the Calabrian Trench and Central and Western Sicily are the lowest (minimum M ≥ 6.5 recurrence times of 550–800 years). Most zones are probably capable of generating earthquakes up to magnitudes 7–7.5, with the exception of Central and Western Sicily where maximum events sizes most likely do not exceed 7.  相似文献   

Deep structure of the Nojima Fault, southwest Japan, estimated from borehole observations of fault-zone trapped waves   总被引：1，自引：0，他引：1  

Takashi Mizuno  Kin&#x;ya Nishigami 《Tectonophysics》2006,417(3-4):231-247

To estimate the deep structure of the southern part of the Nojima Fault, southwest Japan without the influence of near-surface structures, we analyzed the Love-wave-type fault-zone trapped waves (LTWs) recorded by a borehole seismometer at 1800 m depth. We examined the polarization, dispersion, and dominant frequency of the wavetrain following the direct S-wave in each seismogram to identify the LTW. We selected eight candidates for typical LTWs from 462 records. Because the duration of the LTW increases with hypocentral distance, we infer that the low velocity fault-zone of the Nojima Fault continues towards the seismogenic depth. In addition, since the duration of the LTW increases nonlinearly with hypocentral distance, we infer that the S-wave velocity of the fault-zone increases with depth. The location of events showing the LTW indicates that the fault-zone dips to the southeast at 75° and continues to a depth of approximately 10 km. We assumed a uniform low-velocity waveguide to estimate the average structure of the fault-zone. We estimated the average width, S-wave velocity, and Q_s of the fault-zone by comparing an analytical solution of the LTW with measured data. The average width, S-wave velocity, and Q_s of the fault-zone are 150 to 290 m, 2.5 to 3.2 km/s, and 40 to 90, respectively. Hence the fault-zone structure with a larger width and smaller velocity reduction than the fault-zone model estimated by previous surface observation is more suitable to represent the average fault-zone structure of the Nojima fault. The present study also indicated that the shallow layers and/or a shallow fault-zone structure drastically changes the characteristics of the LTW recorded at the surface, and therefore cause a discrepancy in the fault-zone model between the borehole observation and surface observation.  相似文献   

On the Importance of Geolithological Features for the Estimate of the Site Response: The Case of Catania Metropolitan Area (Italy)     

G. Lombardo  H. Langer  S. Gresta  R. Rigano  C. Monaco  G. De Guidi 《Natural Hazards》2006,38(3):339-354

The evaluation of seismic site response in the urban area of Catania was tackled by selecting test areas having peculiar lithological and structural features, potentially favourable to large local amplifications of ground motion. The two selected areas are located in the historical downtown and in the northern part of Catania where the presence of a fault is evident. Site response was evaluated using spectral ratio technique taking the horizontal- to-vertical component ratio of ambient noise. Inferences from microtremor measurements are compared with results from synthetic accelerograms and response spectra computed at all drillings available for this area. Such method is particularly suitable in urban areas where the nature of the outcropping geological units is masked by city growth and anthropic intervention on the surface geology. The microtremor H/V spectral ratios evaluated at soft sites located within the downtown profile tend to be smaller than that usually reported in the literature for such soils. A tendency for amplifications to peaks near 2 Hz is observed only in some sites located on recent alluvial deposits. Evidences for amplifications of site effects (frequency range 4–8 Hz) were observed in the sampling sites located on the fault, with a rapid decrease of spectral amplitude just a few tenths of metres away from the discontinuity. Numerical simulations evidenced the importance of geolithological features at depth levels even greater than 20–30 m. Besides this, the results strongly confirm the importance of the subsurface geological conditions, in the estimate of seismic hazard at urban scale.  相似文献