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   

Influence of depositional processes on the geotechnical parameters of Chicago glacial clays   总被引：1，自引：0，他引：1  

C.K. Chung  R.J. Finno   《Engineering Geology》1992,32(4):225-242

The effects of depositional environment on properties, stress history, and undrained and drained shear-strength parameters are evaluated for Chicago glacial clay. Recent geology and basic depositional environments are described. Both laboratory and in-situ shear-strength evaluations have been conducted at several sites in the study area. Results of the investigations indicate that, while depositional environment has a large impact on the engineering properties of these clays, identification of the depositional environment is in itself insufficient to strength parameters. Post-depositional events are shown to alter the stress history imparted during deposition and thus impact shear-strength parameters.  相似文献   

Radium-226 in the eastern equatorial Pacific     

Yu-chia Chung  Harmon Craig 《Earth and Planetary Science Letters》1973,17(2):306-318

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Elasticity and Equations of State of Olivines in the Mg₂SiO₄-Fe₂SiO₄ System     

D. H. Chung 《Geophysical Journal International》1971,25(5):511-538

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Horizontal and vertical distribution of PCBs and chlorinated pesticides in sediments from Masan Bay,Korea   总被引：1，自引：0，他引：1  

Hong SH  Yim UH  Shim WJ  Oh JR  Lee IS 《Marine pollution bulletin》2003,46(2):244-253

Horizontal and vertical distributions of organochlorine compounds (OCs) were determined in sediments from Masan Bay. The concentrations of polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethanes (DDTs), HCB, hexachlorocyclohexanes (HCHs) and chlordane related compounds (CHLs) in sediments were in the range of 1.24-41.4, 0.28-89.2, 0.02-0.59, nd-1.03, and nd-2.56 ng/g, respectively. The spatial distribution of OCs showed a negative gradient from the inner of the bay to outer part of the bay, indicating that the source of OCs was probably located inside the bay. Compositional pattern of PCB congeners showed a relatively high concentration of high-chlorinated congeners in the inner part of the bay and a relatively low concentration of low-chlorinated congeners in the outer part. In sediment core from Masan Bay maximum concentrations of PCBs and DDTs are observed in the subsurface samples and correspond to an age of early 1980s and late 1960s. The concentration profiles of PCBs and DDTs in sediments of Masan Bay appear to correspond to use of PCBs and DDTs in Korea.  相似文献   

Implementation of configuration dependent stiffness proportional damping for the dynamics of rigid multi-block systems     

Yun?Byeong?Chae  Jae?Kwan?KimEmail author 《地震工程与工程振动(英文版)》2003,2(1):87-97

The distinct element method (DEM) has been used successfully for the dynamic analysis of rigid block systems. One of many difficulties associated with DEM is modeling of damping. In this paper, new procedures are proposed for the damping modeling and its numerical implementation in distinct element analysis of rigid multi-block systems. The stiffness proportional damping is constructed for the prescribed damping ratio, based on the non-zero fundamental frequency effective during the time interval while the boundary conditions remain essentially constant. At this time interval, the fundamental frequency can be estimated without complete eigenvalue analysis. The damping coefficients will vary while the damping ratio remains the same throughout the entire analysis. A new numerical procedure is developed to prevent unnecessary energy loss that can occur during the separation phases. These procedures were implemented in the development of the distinct element method for the dynamic analyses of piled multi-block systems. The analysis results for the single-block and two-block systems were in a good agreement with the analytic predictions. Applications to the seismic analyses of piled fourblock systems revealed that the new procedures can make a significant difference and may lead to much-improved results.  相似文献   

Experimental confirmation of the lack of carbon isotope exchange between methane and carbon oxides at high temperatures     

William M. Sackett  H.Moses Chung 《Geochimica et cosmochimica acta》1979,43(2):273-276

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Parametric studies of physical conditions in the Earth's upper mantle     

Dae H. Chung 《Tectonophysics》1980,64(3-4)

Seismic body-wave and surface-wave data indicate the existence of a substantial lowvelocity, low-Q zone in the upper mantle beneath western North America. Conditions in this zone are distinctively different from those that are typical of the upper mantle in shield regions. The present study, using Walsh's model for partially melted rock, suggests a common mechanism for low-velocity and low-Q zones. This parametric study also indicates that the pronounced low-velocity, low-Q zone and anomalous travel-time delays of both P and S waves in the Basin and Range Province are consistent with the combined effects of high temperature, chemical composition, phase changes, and partial melting. The observed low P_n velocity in this region is consistent with high temperature, chemical composition, and the presence of a partially molten layer within the upper mantle, but the observed teleseismic delay times result principally from the thickness of the lowvelocity zone. The teleseismic delay-time variations are therefore related to the seismic Q distribution in the asthenosphere. Conditions a few kilometers beneath the Moho boundary influence the P_n velocity; however, the observed correlation among the teleseismic signal amplitudes, travel-time delays, and the upper mantle Q indicates that the P_n velocity is a better indicator of upper mantle Q than suggested by the P_n path alone. This knowledge of the upper mantle seems to account for the anomalous effects of the Basin and Range Province and other regions of similar tectonic nature on observations of teleseismic events. This will provide a practical technique for comparing seismic observations made in unstable tectonic regions with observations made in shield areas.  相似文献   

A²²⁶Ra section across the East Pacific Rise     

Y. Chung 《Earth and Planetary Science Letters》1980,49(2):319-328

Four vertical Ra profiles have been measured across the East Pacific Rise (EPR) from Callao to Tahiti. These profiles show that Ra in the deep water (below 2 km depth) increases toward the EPR. However, this increase does not necessarily indicate a Ra source on the EPR. The increase from Tahiti toward the EPR reflects the general trend of the Pacific Ra distribution. The decrease from the EPR eastward to the Peru Basin is probably due to the continental effect with higher sedimentation rates.The hydrography, especially potential temperature and oxygen, indicates significant differences below about 3 km depth between the east and west flanks of the EPR indicating the effect of the cold bottom water to the west of the EPR. The benthic front is identified at 3.9 km depth at the westernmost station near Tahiti. Silicate and salinity data are by no means unique and reflect a complicated local circulation and mixing pattern with a minor intrusion of the Antarctic Bottom Water from the south into the Peru Basin.The θ-Ra and Ra-Si relationships both indicate an enrichment of Ra in the deep water below 2 km depth probably due to input from the underlying sediments. Above 2 km depth, Ra covaries almost linearly with θ as well as Si, mimicking a stable conservative property. This suggests that the radiodecay rate is nearly balanced by the input rate within the water column between 1 and 2 km depth in which θ is linearly correlated withS.Simple vertical model calculations show that the in-situ production of Ra by particulate dissolution in the deep water is negligible within a reasonable range of upwelling rates from 2 to 12 m/yr. Thus the Ra profiles show a net decay effect and so the θ-Ra relations are not linear in the deep water. In fact, the composite θ-Ra plots show a break at 25 dpm/100 kg (at 2 km depth) rather than a smooth curve, while theθ-S plots are essentially linear. A maximum Ra production rate of about 8 × 10^?3 (dpm/100 kg) yr^?1 is obtained from all the profiles with minimum upwelling rates between 0.7 and 3.5 m/yr.  相似文献   

²¹⁰Pb and²²⁶Ra distributions in the Circumpolar waters     

Y. Chung 《Earth and Planetary Science Letters》1981,55(2):205-216

²¹⁰Pb and²²⁶Ra profiles have been measured at five GEOSECS stations in the Circumpolar region. These profiles show that²²⁶Ra is quite uniformly distributed throughout the Circumpolar region, with slightly lower activities in surface waters, while²¹⁰Pb varies with depth as well as location or area. There is a subsurface²¹⁰Pb maximum which matches the oxygen minimum in depth and roughly correlates with the temperature and salinity maxima. This²¹⁰Pb maximum has its highest concentrations in the Atlantic sector and appears to originate near the South Sandwich Islands northeast of the Weddell Sea. Concentrations in this maximum decrease toward the Indian Ocean sector and then become fairly constant along the easterly Circumpolar Current.Relative to²²⁶Ra, the activity of²¹⁰Pb is deficient in the entire water column of the Circumpolar waters. The deficiency increases from the depth of the²¹⁰Pb maximum toward the bottom, and the²¹⁰Pb/²²⁶Ra activity ratio is lowest in the Antarctic Bottom Water, indicating a rapid removal of Pb by particulate scavenging in the bottom layer and/or a short mean residence time of the Antarctic Bottom Water in the Circumpolar region.²²⁶Ra is essentially linearly correlated with silica and barium in the Circumpolar waters. However, close examination of the vertical profiles reveals that Ba and Si are more variable than²²⁶Ra in this region.  相似文献