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排序方式: 共有1013条查询结果,搜索用时 15 毫秒
41.
苏北溱潼凹陷的拉张量研究及构造运动强度分析 总被引:3,自引:0,他引:3
运用正演平衡剖面方法,本文对苏北溱潼凹陷三条剖面的演化过程进行了模拟,恢复计算出各断层各期次的伸展量,该箕状凹陷各发展阶段的拉张量以及对应于三期主要构造运动的拉张量。结果表明,构造运动具有延续性,仅在某些组段的表现更为强烈。在时空上,拉张活动具有很大的不均衡性,在凹陷的西南部,中部及东北部地区,拉张量及沉积特征均有很大差异,构造运动的强度也各不相同。 相似文献
42.
43.
本文对如何利用强震加速度记录测定近震震级ML的问题进行了研究,指出了在我国所使用的原始量规函数存在着系统偏差,并用回归现有观测资料的方法修正了这种系统偏差。用修正后的量规函数,利用近场加速度记录计算的ML值同微震台网所测定的值符合得较好,说明本文所提出的方法是可行的。 相似文献
44.
Katsuyuki Abe 《Pure and Applied Geophysics》1995,144(3-4):735-745
The Hokkaido-Nansei-Oki earthquake (M
w
7.7) of July 12, 1993, is one of the largest tsunamigenic events in the Sea of Japan. The tsunami magnitudeM
t
is determined to be 8.1 from the maximum amplitudes of the tsunami recorded on tide gauges. This value is larger thanM
w
by 0.4 units. It is suggested that the tsunami potential of the Nansei-Oki earthquake is large forM
w
. A number of tsunami runup data are accumulated for a total range of about 1000 km along the coast, and the data are averaged to obtain the local mean heightsH
n
for 23 segments in intervals of about 40 km each. The geographic variation ofH
n
is approximately explained in terms of the empirical relationship proposed byAbe (1989, 1993). The height prediction from the available earthquake magnitudes ranges from 5.0–8.4 m, which brackets the observed maximum ofH
n
, 7.7 m, at Okushiri Island. 相似文献
45.
The paper studies the effect of magnitude errors on heterogeneous catalogs, by applying the apparent magnitude theory (seeTinti andMulargia, 1985a), which proves to be the most natural and rigorous approach to the problem. Heterogeneities in seismic catalogs are due to a number of various sources and affect both instrumental as well as noninstrumental earthquake compilations.The most frequent basis of heterogeneity is certainly that the recent instrumental records are to be combined with the historic and prehistoric event listings to secure a time coverage, considerably longer than the recurrence time of the major earthquakes. Therefore the case which attracts the greatest attention in the present analysis is that of a catalog consisting of a subset of higher quality data, generallyS
1, spanning the interval T
1 (the instrumental catalog), and of a second subset of more uncertain magnitude determination, generallyS
2, covering a vastly longer interval T
2 (the historic and/or the geologic catalog). The magnitude threshold of the subcatalogS
1 is supposedly smaller than that ofS
2, which, as we will see, is one of the major causes of discrepancy between the apparent magnitude and the true magnitude distributions. We will further suppose that true magnitude occurrences conform to theGutenberg-Richter (GR) law, because the assumption simplified the analysis without reducing the relevancy of our findings.The main results are: 1) the apparent occurrence rate exceeds the true occurrence rate from a certain magnitude onward, saym
GR; 2) the apparent occurrence rate shows two distinct GR regimes separated by an intermediate transition region. The offset between the two regimes is the essential outcome ofS
1 being heterogeneous with respect toS
2. The most important consequences of this study are that: 1) it provides a basis to infer the parameters of the true magnitude distribution, by correcting the bias deriving from heterogeneous magnitude errors; 2) it demonstrates that the double GR decay, that several authors have taken as the incontestable proof of the failure of the GR law and of the experimental evidence of the characteristic earthquake theory, is instead perfectly consistent with a GR-type seismicity. 相似文献
46.
印尼苏门答腊8.7级大震对中国陆区的影响 总被引:16,自引:1,他引:16
发生在2004年12月26日的印尼苏门答腊8.7级地震,是全球有地震台网以来100多年中记录到的少数几次特大地震之一。初步汇集了在中国陆区观测到的地震活动、地壳形变、地下流体等多学科震时和震后效应的异常变化,包括地震活动性(特别是云南地区)的显著增强;地壳形变观测,尤其是钻孔应变观测记录到地壳应力-应变的震时和震后显著变化,以及地下水温度、化学成分、特别是水位的突出变化。同时,还从库仑破裂应力触发、动态应力触发以及下地壳和上地幔流动变形机制等方面,对这些大震效应作了一些成因机理讨论。 相似文献
47.
Numerical simulation of groundwater flowing to horizontal seepage wells under a river 总被引:6,自引:0,他引:6
A horizontal seepage well, consisting of an interconnected vertical well, galleries, chambers and small-diameter radiating
bores, is used to acquire relatively clean water that has been filtered through natural alluvial deposits in a riverbed. It
has wide application, especially in arid and semi-arid areas. The lack of calculation formulae or models for horizontal seepage
wells, up until now, has resulted in several false applications. Based on the analysis of groundwater flow characteristics,
it has been concluded that several flow regimes coexist and hydraulic head loss exists in the horizontal seepage well. To
avoid the difficulty of confirming the flux or head distribution in such a complex system, the model boundary of the whole
horizontal seepage well has been moved to that of just the vertical well, and the well-aquifer system was treated as a heterogeneous
medium, where the horizontal seepage well itself is a highly permeability medium. A mathematical model has been developed,
based on the coupled seepage-pipe flow, by the introduction of equivalent hydraulic conductivity according to different flow
regimes. Then a three-dimensional finite difference numerical model, based on the mathematical model, was developed and applied
to a horizontal seepage well in China. The numerical model verified the groundwater flow characteristics of the horizontal
seepage well.
An erratum to this article can be found at 相似文献
48.
Yih-Min Wu Hiroo Kanamori Richard M. Allen Egill Hauksson 《Geophysical Journal International》2007,170(2):711-717
We explore a practical approach to earthquake early warning in southern California by determining a ground-motion period parameter τ c and a high-pass filtered displacement amplitude parameter Pd from the initial 3 s of the P waveforms recorded at the Southern California Seismic Network stations for earthquakes with M > 4.0. At a given site, we estimate the magnitude of an event from τ c and the peak ground-motion velocity ( PGV ) from Pd . The incoming three-component signals are recursively converted to ground acceleration, velocity and displacement. The displacements are recursively filtered with a one-way Butterworth high-pass filter with a cut-off frequency of 0.075 Hz, and a P -wave trigger is constantly monitored. When a trigger occurs, τ c and Pd are computed. We found the relationship between τ c and magnitude ( M ) for southern California, and between Pd and PGV for both southern California and Taiwan. These two relationships can be used to detect the occurrence of a major earthquake and provide onsite warning in the area around the station where onset of strong ground motion is expected within seconds after the arrival of the P wave. When the station density is high, the methods can be applied to multistation data to increase the robustness of onsite early warning and to add the regional warning approach. In an ideal situation, such warnings would be available within 10 s of the origin time of a large earthquake whose subsequent ground motion may last for tens of seconds. 相似文献
49.
Prantik Mandal R. K. Chadha N. Kumar I. P. Raju C. Satyamurty 《Pure and Applied Geophysics》2007,164(10):1963-1983
During the last six years, National Geophysical Research Institute, Hyderabad has established a semi-permanent seismological
network of 5–8 broadband seismographs and 10–20 accelerographs in the Kachchh seismic zone, Gujarat with a prime objective
to monitor the continued aftershock activity of the 2001 Mw 7.7 Bhuj mainshock. The reliable and accurate broadband data for the 8 October Mw 7.6 2005 Kashmir earthquake and its aftershocks from this network as well as Hyderabad Geoscope station enabled us to estimate
the group velocity dispersion characteristics and one-dimensional regional shear velocity structure of the Peninsular India.
Firstly, we measure Rayleigh-and Love-wave group velocity dispersion curves in the period range of 8 to 35 sec and invert
these curves to estimate the crustal and upper mantle structure below the western part of Peninsular India. Our best model
suggests a two-layered crust: The upper crust is 13.8 km thick with a shear velocity (Vs) of 3.2 km/s; the corresponding values
for the lower crust are 24.9 km and 3.7 km/sec. The shear velocity for the upper mantle is found to be 4.65 km/sec. Based
on this structure, we perform a moment tensor (MT) inversion of the bandpass (0.05–0.02 Hz) filtered seismograms of the Kashmir
earthquake. The best fit is obtained for a source located at a depth of 30 km, with a seismic moment, Mo, of 1.6 × 1027 dyne-cm, and a focal mechanism with strike 19.5°, dip 42°, and rake 167°. The long-period magnitude (MA ~ Mw) of this earthquake is estimated to be 7.31. An analysis of well-developed sPn and sSn regional crustal phases from the bandpassed
(0.02–0.25 Hz) seismograms of this earthquake at four stations in Kachchh suggests a focal depth of 30.8 km. 相似文献
50.