共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
3.
4.
This paper describes the problems concerning the relation between intensity and magnitude, which are substantially different quantities by nature. In consideration of the necessity to translate magnitude values into intensity values, andvice versa, to find magnitude values for historical earthquakes, we have searched for a correspondence that may exist between intensity and magnitude, hypothesising that magnitude values were distributed as a known function. Therefore, we have analysed two distribution functions, first the Gaussian distribution, then a box function, of which the goodness of fit has been estimated by the 2 test. In conclusion, the probability distribution of magnitude vs intensity seems better described by a Gaussian curve. 相似文献
5.
6.
7.
V. K. Lemzikov 《Journal of Volcanology and Seismology》2014,8(2):125-134
This study makes use of spectral models for tectonic earthquakes in application to volcano-tectonic (VT) and deep-focus long period volcanic (DL) earthquakes. For these earthquakes we adjusted the parameters of source spectra, and simultaneously, the medium where seismic waves propagate. We derived preliminary results to characterize the models of source spectra for volcanic earthquakes that occur on Klyuchevskoi Volcano. This method can also be used to estimate the attenuation parameters of seismic waves, which are important for the assessment of stress and strain in a volcanic medium. 相似文献
8.
B. T. Brady 《Pure and Applied Geophysics》1976,114(1):119-139
A theory of deep earthquakes, termed the inclusion collapse theory, is proposed in this paper. In the inclusion theory of crustal (or shallow) earthquakes, faults were shown to terminate within an inclusion zone. This zone represents a region within the brittle portion of the lithospheric plate that contains open cracks (voids) of varying sizes that, to a first order approximation, are uniformly distributed throughout the inclusion zone. When the lithospheric plate containing these faults and their associated inclusions is subducted into the mantle, the stress normal to the fault planes must increase. A depth is eventually reached where slippage along the fault planes is no longer possible. Earthquakes are postulated to occur at a specified depth within the mantle as a result of processes leading to collapse of these voids.When the long-term modulus of the plate is much greater than the long-term modulus of the mantle, large pressures are shown to develop within the plate during periods of active subduction. These pressures are shown to be sufficient to initiate partial collapse of voids of similar geometry throughout the inclusion zone.The inclusion collapse theory and the concentration of pressure within the plate lead to four results. (1) Earthquakes that are produced by a void collapse mechanism will not occur below a subduction depth calculated to be between 350 and 1000 km (2) The physical process most likely responsible for producing void collapse is the formation of shear, melt zones whose thicknesses are on the order of 1 to 10 cm in the immediate vicinity of the voids. This mechanism, is shown to produce a precursor time on the order of a few hundred seconds during which there is a release of shear strain prior to the earthquake. (3) The maximum energy released by void collapse is independent of the source depth. (4) The number of earthquakes produced by this process will decrease hyperbolically with source depth. Source depth, in the context used in this article, refers to the depth in the mantle to the inclusion zone where voids of similar geometry are undergoing partial collapse. The maximum source depth refers to the depth where all voids have closed. 相似文献
9.
Summary The focal mechanisms of two Peruvian earthquakes, January 15, 1958, and January 13, 1960, are determined using data from both the first motion ofP and the polarization ofS. The fault motions correspond to strike slip motion on neighboring faults corresponding in strike to geophysical evidences of regional faulting. The motion is left lateral in one of the shocks, right lateral in the other. 相似文献
10.
We useP andS times listed in the International Seismological Summary to relocate 23 historical earthquakes (1927–1963) reported as occurring at or below 670 km. In all cases, our relocated hypocenters are shallower than the starting depths; furthermore, all events converge to 691 km or less, with a precision estimated at ±10 km. This study upholds the results of Stark and Frohlich, who had usedpP–P times of post-WWSSN earthquakes to constrain reliable hypocentral depths to no greater than 684 km. In particular, we reject Rothé's claim that a 1963 event in the vicinity of New Guinea occurred at a depth of more than 780 km. 相似文献
11.
12.
中等地震活动增强作为强震标志的研究 总被引:7,自引:0,他引:7
通过对(1990~1996年)发生在我国大陆及边境地区24次6级以上地震的分析研究表明,80%的强震主震前在震源区及附近有中等地震活动增强的过程。异常表现出共同的基本特征,即长期平静→增强活动→震前平静→发震。震前平静至发震大约经历几个月到2年时间(平均10个月左右),可以作为中短期地震预报判据。用岩石蠕变声发射实验来解释这一现象,可把中等地震活动增强看作是稳态蠕变阶段后期发生的广义前震。 相似文献
13.
The gutenberg-richter law for earthquakes in air pollution episodes: A case study for Athens, Greece 总被引:1,自引:0,他引:1
Maria Efstathiou Chris Tzanis Costas Varotsos Despina Deligiorgi 《Acta Geophysica》2012,60(1):280-290
The main aim of this study is to investigate whether the main components of the photochemical smog episodes over megacities
obey the Gaussian distribution or do they follow the distribution of the Gutenberg-Richter law. To this end, a case study
has been implemented for Athens, Greece, which is among the most densely populated capitals in the middle latitudes of the
Northern Hemisphere. The data employed are hourly mean values of surface ozone and nitrogen dioxide concentrations collected
by the National Air Pollution Monitoring Network during the period 1988–2008. The results obtained show that the surface ozone
and nitrogen dioxide concentrations obey the Gutenberg-Richter law, while their extreme values follow the Generalized Pareto
distribution. This finding is important for current efforts to reliably forecast the air pollutants concentrations and to
quantify their contribution to climate change. Finally, the plausible mechanisms involved in air pollution dynamics leading
to the above-mentioned behaviour are also discussed, assuming the air pollution system governed by non-linear processes. 相似文献
14.
将全球分为15个研究区,用1900~2009年MW≥7.0地震目录,统计分析了各区大地震与月球交点运动周期的关系,得出15个研究区中有10个区,大地震存在统计意义上的18.6 a周期:活跃段为12.4 a,平静段为6.2 a;环太平洋地震带北、南、西、东4大区的大地震,不仅有这样的周期,而且其地震活跃段的时间存在一定规律.用第6个18.6 a(1991~2009年)期间的大地震,检验据前5个18.6 a(1900~1990年)地震目录所得18.6 a 周期的稳定性和实用性,发现有这种周期的地区多数的周期性是稳定的.大地震18.6 a周期的可能成因有: (1)18.6 a潮波通过调制日潮和半日潮调制大地震; (2)上地幔内流体的潮汐(地内潮)作用; (3)18.6 a潮波通过影响地球自转变化调制大地震. 相似文献
15.
A.M. Dziewonski A. Friedman D. Giardini J.H. Woodhouse 《Physics of the Earth and Planetary Interiors》1983,33(2):76-90
The centroid-moment tensor analysis is applied to digital recordings of 308 moderate and large earthquakes that occurred during 1982 and were recorded by the Global Digital Seismograph Network (GDSN) and International Deployment of Accelerometers (IDA) networks. The tables contain numerical results for all events. A graphical representation of the source geometry is shown for the full moment tensor solution, as well as for the “best double couple”. 相似文献
16.
J.H. Ansell 《Physics of the Earth and Planetary Interiors》1978,17(2):P1-P6
In regions, such as subduction zones, with systematic velocity variations from the travel-time model, the estimated hypocentres may be significantly mislocated and the estimated hypocentres may depend strongly on the stations and phases used. The estimated depths of earthquakes beneath the North Island, New Zealand, as determined by the International Seismological Centre and the New Zealand Seismological Observatory are used to illustrate this effect. Compared with ISC depths determined using local P phases only, the NZSO depths using local P and S phases are shallower by about 15 km while ISC depths using local and releseismic P phases are shallower again by about 30 km (and up to 70 km). Thus ISC depths which do not use teleseismic observations are not consistent with those which do and so care must be exercised when using both types of solution. 相似文献
17.
《Earth and Planetary Science Letters》2007,253(3-4):485-496
Seismic hazard is difficult to assess in regions of low strain rates. A major limitation often relates to the absence of large instrumentally recorded events precluding any comparison between seismological data and paleoseismic or morphotectonic informations. We take advantage of the 1904 Ms∼7.1 earthquake that struck the southern edge of stable Eurasia and investigate if morphotectonic and paleoseismic observations can provide a reliable estimate of the seismic potential of slow-slipping faults. We have conducted a paleoseismic study of the Krupnik normal fault thought to be responsible for the event. A section of the fault bearing remnants of a 2 m-high scarp has been selected at the base of triangular facets. The trenching site locates where the scarp cuts across colluviums washed from the bedrock facetted slopes. We excavated two neighbouring trenches, one across a well-preserved portion of the scarp, and one across a portion degraded by a landslide. The excavations reveal a set of coarse colluvial units faulted against bedrock and affected by secondary fissures. Faulting appears to have resulted from a single event with normal throw greater than 1.3 m that occurred before the emplacement of the landslide. Accelerator Mass Spectrometry (AMS) radiocarbon dates of charcoal samples are consistent with the interpretation that the Krupnik Fault slipped recently, most probably in 1904, after a long lasting (> 10 ka) period of quiescence. The morphotectonic and paleoseismic observations yield seismic moment estimates compatible with the instrumental magnitude of the event and indicate that destructive and infrequent earthquakes typify the regional seismic behaviour. 相似文献
18.
An interpretation of the source origin of the largest Transcaspian Kazandzhik 1946 and Krasnovodsk 1895 earthquakes is proposed. The interpretation is based on the analysis of data on the geological structure of the Transcaspian region and the available evidence for coseismic effects of these events. Data on other earthquakes of the region and the results of focal mechanism determinations are taken into account. The Kazandzhik earthquake consisted of two shocks with separate sources. The source of the first, weaker shock, located in structures of the Greater Balkhan Ridge, was characterized by reversed-strike-slip motions. The 40–50-km-long source of the second, main shock, which determined the earthquake magnitude (M ~ 6.9–7.0), was located in the Kazandzhik basin, in the boundary zone between the Kopet Dagh foredeep and the Frontal anticlinal range. It was similar in type and coseismic effects to the source of the Ashkhabad earthquake of 1948. The Krasnovodsk earthquake source 100–120 km long, located in the crust, is associated with the development of the Balkhan foredeep. In accordance with the source size, the magnitude of the Krasnovodsk earthquake is M ~ 7.8–8.0. The three major earthquakes (Ashkhabad, Kazandzhik, and Krasnovodsk) in the Transcaspian region are associated with the general tectonic process of the presently continuing development of the Transcaspian Kopet Dagh and Balkhan foredeeps. This process forms the major Transcaspian seismogenic zone, possibly extending through the Caspian Sea up to the Black Sea coast. The Transcaspian seismogenic zone of a smaller size is associated with the continuing development of domelike structures of the Pribalkhano—Livanovskaya anticlinal zone in the Pribalkhanskaya depression. The generation of such earthquakes as the Kum Dagh 1983 and the Nebit Dagh (Burun) 1984 earthquakes is associated with this zone. 相似文献
19.
Large magnitude earthquakes generated at source–site distances exceeding 100km are typified by low‐frequency (long‐period) seismic waves. Such induced ground shaking can be disproportionately destructive due to its high displacement, and possibly high velocity, shaking characteristics. Distant earthquakes represent a potentially significant safety hazard in certain low and moderate seismic regions where seismic activity is governed by major distant sources as opposed to nearby (regional) background sources. Examples are parts of the Indian sub‐continent, Eastern China and Indo‐China. The majority of ground motion attenuation relationships currently available for applications in active seismic regions may not be suitable for handling long‐distance attenuation, since the significance of distant earthquakes is mainly confined to certain low to moderate seismicity regions. Thus, the effects of distant earthquakes are often not accurately represented by conventional empirical models which were typically developed from curve‐fitting earthquake strong‐motion data from active seismic regions. Numerous well‐known existing attenuation relationships are evaluated in this paper, to highlight their limitations in long‐distance applications. In contrast, basic seismological parameters such as the Quality factor (Q‐factor) could provide a far more accurate representation for the distant attenuation behaviour of a region, but such information is seldom used by engineers in any direct manner. The aim of this paper is to develop a set of relationships that provide a convenient link between the seismological Q‐factor (amongst other factors) and response spectrum attenuation. The use of Q as an input parameter to the proposed model enables valuable local seismological information to be incorporated directly into response spectrum predictions. The application of this new modelling approach is demonstrated by examples based on the Chi‐Chi earthquake (Taiwan and South China), Gujarat earthquake (Northwest India), Nisqually earthquake (region surrounding Seattle) and Sumatran‐fault earthquake (recorded in Singapore). Field recordings have been obtained from these events for comparison with the proposed model. The accuracy of the stochastic simulations and the regression analysis have been confirmed by comparisons between the model calculations and the actual field observations. It is emphasized that obtaining representative estimates for Q for input into the model is equally important.Thus, this paper forms part of the long‐term objective of the authors to develop more effective communications across the engineering and seismological disciplines. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
20.
A. Ya. Sidorin 《Seismic Instruments》2011,47(1):89-92
A 15-min periodicity of seismic events in the catalog of earthquakes in Greece is discovered. It is most vividly expressed
in the time series of weak and shallow events; however, it also occurs in the series of rather strong representative and deep
earthquakes. 相似文献