中国东南沿海地震带大震重复性和大震减震作用   总被引：2，自引：0，他引：2  

陈家超  冯霞英 《华南地震》1992,12(3):29-35

本文从物质分异的角度出发并利用现代小震活动资料,讨论了东南沿海地震带历史大震震源区及其附近,今后一段历史时期内是否有大震(M≥0)震源区大震重复性和大震减震作用问题。结果表明,这些历史震源区目前还处在减震阶段,今后一段时间只能以小震或中强地震的活动特点来显示这一弱化区。  相似文献   

世界早期历史地震史料的比较研究(待续)     

郭履灿  高建国  阎维彰 《山西地震》1992,(2)

通过对各国地震最早记载及其背景性证据的分析;用时间差分序列的双对数法,进行了地震记载资料丰富程度的探讨;研究了3700年前的全球地震活跃期;给出了公元前2221年至公元1900年105个国家(地区)的资料。  相似文献   

Coda-Q before and after the 1986 Andreanof Islands earthquake     

Zhong-Xian Huang  Carl Kisslinger 《Pure and Applied Geophysics》1992,138(1):1-16

Coda-Q values before and after the May 7, 1986 Andreanof Islands earthquake in the central Aleutian subduction zone were calculated from microearthquake seismograms on the basis of Aki's single backscattering model. Digital waveforms from 329 microeathquakes in 5.4 years before the mainshock and 40 aftershocks recorded by 11 stations of the Central Aleutians Seismic Network were utilized. Before the mainshock, coda-Q in the rupture zone west of the mainshock epicenter was 15% higher than theQ outside the rupture zone to the west. A lowQ in the region east of the mainshock epicenter is inferred, but lacks solid evidence. The highQ region accords with the part of the rupture zone where most seismic moment was released. During approximately two months after the mainshock, coda-Q in the rupture zone decreased about 10%. PrecursoryQ changes were not found in the 5.4 years before the mainshock. It is deduced that a coda-Q precursor, if it existed, was of small magnitude (<10%), or its duration was either shorter than one year or longer than four years.  相似文献   

The reservoir-associated earthquakes of April 1983 in western Thailand: Source modeling and implications for induced seismicity     

Wai-Ying Chung  Chao Liu 《Pure and Applied Geophysics》1992,138(1):17-41

On 22 April 1983, a very large area of Thailand and part of Burma were strongly shaken by a rare earthquake (m _b=5.8,M _s=5.9). The epicenter was located at the Srinagarind reservoir about 190 km northwest of Bangkok, a relatively stable continental region that experienced little previous seismicity. The main shock was preceded by some foreshocks and followed by numerous aftershocks. The largest foreshock ofm _b=5.2 occurred 1 week before the main shock, and the largest aftershock ofm _b=5.3 took place about 3 hours after the main shock. Focal mechanisms of the three largest events in this earthquake sequence have been studied by other seismologists using firts-motion data. However, the solutions for the main shock and the largest aftershock showed significant inconsistency with known surface geology and regional tectonics. We reexamined the mechanisms of these three events by using teleseismicP-andS-waveforms and through careful readings ofP-wave first motions. The directions of theP axes in our study range from NNW-SSE to NNE-SSW, and nodal planes strike in the NW-SE to about E-W in agreement with regional tectonics and surface geology. The main shock mechanism strikes 255°, dips 48°, and slips 63.5°. The fault motions during the main shock and the foreshock are mainly thrust, while the largest aftershock has a large strike-slip component. The seismic moment and the stress drop of the mainshock are determined to be 3.86×10²⁴ dyne-cm and 180 bars, respectively. The occurrence of these thrust events appears to correlate with the unloading of the Srinagarind reservoir. The focal depths of the largest foreshock, the main shock, and the largest aftershock are determined to be 5.4 km, 8 km, and 22.7 km, respectively, from waveform modeling and relative location showing a downward migration of hypocenters of the three largest events during the earthquake sequence. Other characteristics of this reservoir-induced earthquake sequence are also discussed.  相似文献   

Triggered earthquakes and deep well activities   总被引：1，自引：0，他引：1  

Craig Nicholson  Robert L. Wesson 《Pure and Applied Geophysics》1992,139(3-4):561-578

Earthquakes can be triggered by any significant perturbation of the hydrologic regime. In areas where potentially active faults are already close to failure, the increased pore pressure resulting from fluid injection, or, alternatively, the massive extraction of fluid or gas, can induce sufficient stress and/or strain changes that, with time, can lead to sudden catastrophic failure in a major earthquake. Injection-induced earthquakes typically result from the reduction in frictional strength along preexisting, nearby faults caused by the increased formation fluid pressure. Earthquakes associated with production appear to respond to more complex mechanisms of subsidence, crustal unloading, and poroelastic changes in response to applied strains induced by the massive withdrawal of subsurface material. As each of these different types of triggered events can occur up to several years after well activities have begun (or even several years after all well activities have stopped), this suggests that the actual triggering process may be a very complex combination of effects, particularly if both fluid extraction and injection have taken place locally. To date, more than thirty cases of earthquakes triggered by well activities can be documented throughout the United States and Canada. Based on these case histories, it is evident that, owing to preexisting stress conditions in the upper crust, certain areas tend to have higher probabilities of exhibiting such induced seismicity.  相似文献   

Use of the mantle magnitudeM m for the reassessment of the moment of historical earthquakes     

Emile A. Okal 《Pure and Applied Geophysics》1992,139(1):59-85

The mantle magnitudeM _m is used on a dataset of more than 180 wavetrains from 44 large shallow historical earthquakes to reassess their moments, which in many cases had been previously estimated only on the basis of the earthquake's rupture area. We provide 27 new or revised values ofM _o, based on the spectral amplitudes of surface waves recorded at a number of stations, principally Uppsala and Pasadena. Among them, and most significantly, we document a large low-frequency component to the source of the 1923 Kanto earthquake: the low-frequency seismic moment is 2.9×10²⁸ dyn-cm, in accord with geodetic observations. On the other hand, we revise downwards the seismic moment of the 1906 Ecuador event, which did not exceed 6×10²⁸ dyn-cm.Finally, the study of the 1960 Chilean and 1964 Alaskan earthquakes whose exceptionally large moments are properly retrieved throughM _m measurements, serves proof that this approach performs flawlessly even for the very greatest earthquakes, and is therefore successful in its goal to avoid the saturation effects plaguing any magnitude scale measured at a fixed period.  相似文献   

Chaotic seismic faulting with a mass-spring model and velocity-weakening friction     

Jie Huang  D. L. Turcotte 《Pure and Applied Geophysics》1992,138(4):569-589

We present a systematic analysis of the dynamical behavior introduced by fault zone heterogeneities, using a simple mass-spring model with velocity-weakening friction. The model consists of two sliding blocks coupled to each other and to a constant velocity driver by clastic springs. The state of this system can be characterized by the positions of the two blocks relative to the driver. Symmetry stabilizes the system and generates only cyclic behavior. For an asymmetric system where the frictional forces for the two blocks are not equal, the solutions exhibit chaotic behavior. The transition from stable cyclic behavior to chaos is characterized by the period-doubling route to chaos. Lyapunov exponents are computed to quantify the deterministic chaos and to locate the onset of the chaotic evolution in parameter space. In many examples of deterministic chaos, chaotic behavior of a low-order system implies chaos in similar higher order systems. Thus, our results provide substantial evidence that crustal deformation is an example of deterministic chaos.  相似文献   

东北深,浅源地震的相关活动   总被引：1，自引：0，他引：1  

朱兆才 《地震地磁观测与研究》1992,13(4):20-24

本文讨论了东北深、浅源地震在时间上、强度上的相关活动特点,认为东北地震是太平洋板块俯冲与亚欧板块挤压作用的结果。东北深震超前于浅源地震活动,可为浅源地震监测预报提供信息。  相似文献   

Tomographic study of local earthquake data from the Lake Bogoria region of the Kenya Rift Valley     

J. A. Tongue 《Geophysical Journal International》1992,109(2):249-258

  相似文献   

A cellular-automata, slider-block model for earthquakes II. Demonstration of self-organized criticality for a 2-D system     

Jie Huang  Galina Narkounskaia  Donald L. Turcotte 《Geophysical Journal International》1992,111(2):259-269

  相似文献