Ground-water radon anomaly before the kobe earthquake in Japan

Radon concentration in ground water increased for several months before the 1995 southern Hyogo Prefecture (Kobe) earthquake on 17 January 1995. From late October 1994, the beginning of the observation, to the end of December 1994, radon concentration increased about fourfold. On 8 January, 9 days before the earthquake, the radon concentration reached a peak of more than 10 times that at the beginning of the observation, before starting to decrease. These radon changes are likely to be precursory phenomena of the disastrous earthquake.     

Recent earthquake prediction research in Japan

Japan has experienced many major earthquake disasters in the past. Early in this century research began that was aimed at predicting the occurrence of earthquakes, and in 1965 an earthquake prediction program was started as a national project. In 1978 a program for constant monitoring and assessment was formally inaugurated with the goal of forecasting the major earthquake that is expected to occur in the near future in the Tokai district of central Honshu Island. The issue of predicting the anticipated Tokai earthquake is discussed in this article as well as the results of research on major recent earthquakes in Japan-the Izu earthquakes (1978 and 1980) and the Japan Sea earthquake (1983).     

The oaxaca, Mexico, earthquake of 29 november 1978: a preliminary report on aftershocks

Aftershocks of the 29 November 1978 Oaxaca, Mexico, earthquake (surface-wave magnitude Ms = 7.8) define a rupture area of about 6000 square kilometers along the boundary of the Cocos sea-plate subduction. This area had not ruptured in a large (Ms >/= 7), shallow earthquake since the years 1928 and 1931 and had been designated a seismic "gap." The region has also been seismically quiet for small to moderate (M >/= 4), shallow (depth 相似文献   

Tilt and seismicity changes in the shumagin seismic gap

Changes in the ground surface tilt and in the rate of seismicity indicate that an aseismic deformation event may have occurred between 1978 and 1980 along the plate boundary in the eastern Aleutians, Alaska, within the Shumagin seismic gap. Pavlof Volcano was unusually quiescent during this period. The proposed event would cause an increase of stress on the shallow locked portion of the plate boundary, bringing it closer to rupture in a great earthquake.     

Tomography of the Source Area of the 1995 Kobe Earthquake: Evidence for Fluids at the Hypocenter?

Seismic tomography revealed a low seismic velocity (-5%) and high Poisson's ratio (+6%) anomaly covering about 300 square kilometers at the hypocenter of the 17 January 1995, magnitude 7.2, Kobe earthquake in Japan. This anomaly may be due to an overpressurized, fluid-filled, fractured rock matrix that contributed to the initiation of the Kobe earthquake.     

Postprandial changes in the exhalation rate of radon produced in vivo

The rate of exhalation of radon by persons with long-standing radium burdens increases about twofold shortly after a meal. The increase is short-lived and "normal" values are regained in 1.5 to 2 hours. The effect may account in part for the poor reproducibility in estimates of the freely emanating part of the radium content.     

Detection of radon emanation from the crater aristarchus by the apollo 15 alpha particle spectrometer

The alpha particle spectrometer aboard the Apollo 15 command/service module was designed to detect alpha particles from radon decay and to locate regions with unusual activity on the moon. A significant increase in radon-222 activity was detected from a region containing the crater Aristarchus. The result is interpreted as probably indicating internal activity at the site. By analogy with terrestrial processes, increased radon emanation may be associated with the emission of other volatiles.     

The magnitude 6.7 northridge, california, earthquake of 17 january 1994

The most costly American earthquake since 1906 struck Los Angeles on 17 January 1994. The magnitude 6.7 Northridge earthquake resulted from more than 3 meters of reverse slip on a 15-kilometer-long south-dipping thrust fault that raised the Santa Susana mountains by as much as 70 centimeters. The fault appears to be truncated by the fault that broke in the 1971 San Fernando earthquake at a depth of 8 kilometers. Of these two events, the Northridge earthquake caused many times more damage, primarily because its causative fault is directly under the city. Many types of structures were damaged, but the fracture of welds in steel-frame buildings was the greatest surprise. The Northridge earthquake emphasizes the hazard posed to Los Angeles by concealed thrust faults and the potential for strong ground shaking in moderate earthquakes.     

Atmospheric burnup of the cosmos-954 reactor

On 24 January 1978 the Russian satellite Cosmos-954 reentered the atmosphere over northern Canada. By use of high-altitude balloons, the atmosphere was sampled during 1978 up to an altitude of 39 kilometers to detect particulate debris from the reactor on board the satellite. Enriched uranium-bearing aerosols at concentrations and particle sizes compatible with partial burnup of the Cosmos-954 reactor were detected only in the high polar stratosphere.     

Teleseismic detection of a slow precursor to the great 1989 macquarie ridge earthquake

Low-frequency spectra for the 1989 Macquarie Ridge earthquake (magnitude 8.2) show an amplitude increase and a phase-delay decrease below 6 millihertz that require a short-term slow precursor. This earthquake can be modeled as a compound event in which a fast-rupturing, ordinary earthquake was initiated by an episode of slow, smooth deformation that began more than 100 seconds before the main shock. The moment released in the slow precursor was large, about 3 x 10(20) newton-meters, equivalent to an event of magnitude 7.6. The data are consistent with the precursor being generated in a region of the oceanic upper mantle below the main rupture.     

Detection and monitoring of ongoing aseismic slip in the Tokai region,central Japan

Analysis of global positioning system data shows that the rate of crustal deformations in the Tokai region of Japan, a seismic gap area, changed over the past 18 months. Kalman filtering analysis shows aseismic slip on the plate boundary in the western Tokai region centered on Lake Hamana, adjacent to the anticipated Tokai earthquake source area. The cumulative moment magnitude reaches 6.7 in June 2002 with a relative slip increase northeast of Lake Haman from January 2002. An existence of aseismic slip in the western Tokai supports the hypothesis of a silent event as the cause of uplifting several days before the 1944 Tonankai earthquake.     

Change in the probability for earthquakes in Southern California due to the Landers magnitude 7.3 earthquake

The Landers earthquake in June 1992 redistributed stress in southern California, shutting off the production of small earthquakes in some regions while increasing the seismicity in neighboring regions, up to the present. This earthquake also changed the ratio of small to large events in favor of more small earthquakes within about 100 kilometers of the epicenter. This implies that the probabilistic estimate for future earthquakes in southern California changed because of the Landers earthquake. The location of the strongest increase in probability for large earthquakes in southern California was the volume that subsequently produced the largest slip in the magnitude 7.1 Hector Mine earthquake of October 1999.     

地震前兆的复杂性与地震预报

地震前兆与地震关系的确认是地震预报的关键因素。本文从地震预测和地震前兆异常两个方面系统地介绍了国内外的观测结果和研究成果，并在此基础上初步探讨了前兆异常和地震之间的关系；结合具体的地震观测资料，介绍了地震前兆的多样性以及地震成因的复杂性，进一步阐述了地震预报研究过程中遇到的困难和产生的新问题。     

Forecasting southern california earthquakes

Since 1978 and 1979, California has had a significantly higher frequency of moderate to large earthquakes than in the preceding 25 years. In the past such periods have also been associated with major destructive earthquakes, of magnitude 7 or greater, and the annual probability of occurrence of such an event is now 13 percent in California. The increase in seismicity is associated with a marked deviation in the pattern of strain accumulation, a correlation that is physically plausible. Although great earthquakes (magnitude greater than 7.5) are too infrequent to have clear associations with any pattern of seismicity that is now observed, the San Andreas fault in southern California has accumulated sufficient potential displacement since the last rupture in 1857 to generate a great earthquake along part or all of its length.     

Atmospheric trends in methylchloroform and the global average for the hydroxyl radical

Frequent atmospheric measurements of the anthropogenic compound methylchloroform that were made between 1978 and 1985 indicate that this species is continuing to increase significantly around the world. Reaction with the major atmospheric oxidant, the hydroxyl radical (OH), is the principal sink for this species. The observed mean trends for methylchloroform are 4.8, 5.4, 6.4, and 6.9 percent per year at Aldrigole (Ireland) and Cape Meares (Oregon), Ragged Point (Barbados), Point Matatula (American Samoa), and Cape Grim (Tasmania), respectively, from July 1978 to June 1985. These measured trends, combined with knowledge of industrial emissions, were used in an optimal estimation inversion scheme to deduce a globally averaged methylchloroform atmospheric lifetime of 6.3 (+ 1.2, -0.9) years (1sigma uncertainty) and a globally averaged tropospheric hydroxyl radical concentration of (7.7 +/- 1.4) x 10(5) radicals per cubic centimeter (1sigma uncertainty). These 7 years of gas chromatographic measurements, which comprise about 60,000 individual calibrated real-time air analyses, provide the most accurate estimates yet of the trends and lifetime of methylchloroform and of the global average for tropospheric hydroxyl radical levels. Accurate determination of hydroxyl radical levels is crucial to understanding global atmospheric chemical cycles and trends in the levels of trace gases such as methane.     

Stress diffusion along the san andreas fault at parkfield, california

Beginning in January 1990, the epicenters of microearthquakes associated with a 12-month increase in seismicity near Parkfield, California, moved northwest to southeast along the San Andreas fault. During this sequence of events, the locally variable rate of cumulative seismic moment increased. This increase implies a local increase in fault slip. These data suggest that a southeastwardly diffusing stress front propagated along the San Andreas fault at a speed of 30 to 50 kilometers per year. Evidently, this front did not load the Parkfield asperities fast enough to produce a moderate earthquake; however, a future front might do so.     

四川地震资源与开发研究

界定了地震旅游资源的概念,用灾害经济学观点、旅游规划理论和系统方法分析了"5.12"汶川特大地震派生的地震旅游资源,提出了地震旅游产品开发原则和总体思路,并就龙门山断裂带整个区域地震旅游产品开发的协调互补与整合给出了框架性建议。     

Precursory chemical changes in ground water: kobe earthquake, Japan

Chloride (Cl(-)) and sulfate (SO(4)(2-)) ion concentrations of ground water issuing from two wells located near the epicenter of the Kobe earthquake in Japan fluctuated before the disastrous magnitude 7.2 event on 17 January 1995. The samples measured were pumped ground water packed in bottles and distributed in the domestic market as drinking water from 1993 to April 1995. Analytical results demonstrate that Cl(-)and SO(4)(2-) concentrations increased steadily from August 1994 to just before the earthquake. Water sampled after the earthquake showed much higher Cl(-) and SO(4)(2-) concentrations. The precursory changes in chemical composition may reflect the preparation stage of a large earthquake.     

基于D-InSAR技术的地震形变场获取

阐述了合成孔径雷达干涉测量技术在地震监测方面的历史及现状;指出了"三轨"差分的基本原理;利用ENVISAT数据获取了巴姆地震形变场,并对地震形变结果进行了解译。发现形变主要发生在东面南北方向,南面地表上升约30cm,北面地表下降约18cm。     

2001—2007年四川及周边地区地震时空分布特征

依据中国地震台网实测资料,对四川省及周边地区2001年1月-2007年12月期间4级以上地震进行统计,共计155次,每年平均约22次,同时鉴于汶川大地震余震尚未平息,目前还处于活动期,因此对其单独进行探讨。运用Excel和地理信息系统软件对地震活动的时间序列和空间分布特征进行分析,尝试性地探索其中的规律。结果表明,地震活动在时间分布上存在着明显的季节差异（夏、秋两季的地震活动频率明显高于春、冬两季）和年际变化（2008年为地震活跃期）,在空间分布上地震活动与地质活动构造关系密切,地震主要发生在断裂、断陷带,特别在地块交界处发生率最高。