The northeastern Ohio earthquake of 31 January 1986: Was it induced?
The northeastern Ohio earthquake of 31 January 1986: Was it induced?
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1986 年 1 月 31 日俄亥俄州东北部发生的地震：是诱发的吗？
DOI：
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发表时间：
1988
期刊：
影响因子：
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通讯作者：
R. Wesson
中科院分区：
文献类型：
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作者：
C. Nicholson;E. Roeloffs;R. Wesson
1986年1月31日，美国东部时间11时46分，在俄亥俄州克利夫兰以东约40公里、佩里核电站以南约17公里处发生5.0级地震。包括11个州、哥伦比亚特区和加拿大安大略省部分地区在内的大片地区都有震感，地震在15公里的距离内造成了VI-VII烈度，并在佩里核电站产生了相对较高的短期加速度(0.18克)。截至4月15日，检测到13次余震，其中6次发生在头8天内。有两次余震有震感。余震的震级约为0.5至2.5级。所有地震的震源深度从2公里到6公里不等。除一次小震外，其余余震均呈北东向密集震群。余震的震源机制在N15°~45°E的近垂直节面上表现出以右滑为主的斜向运动，P轴在东北方接近水平。目前有三口深废物处理井在震中区域15公里范围内作业，负责注入近12亿升液体，压力达到环境以上112巴，标称深度为1.8公里。商业水力压裂测量得出的应力估计表明，俄亥俄州东北部的应力状态接近沿有利方向的先前存在的裂缝破坏的理论门槛。这意味着最活跃的两口井底部附近的有效应力条件可能处于或接近早期破坏的临界水平。自1983年以来，距离油井不到5公里的范围内发生了两次地震，可能还发生了三次地震。然而，到主震中心及其余震的相对距离(约12公里)，缺乏许多诱发序列典型的大量小震，该地区在注入开始之前的中小地震的历史，以及压力场随着距离注入井的距离的衰减，所有这些都证明了1986年地震的“自然”起源。相比之下，井底接近破裂条件，以及至少一次地震的可能空间关联，表明不能排除井活动引发的可能性。
Abstract On 31 January 1986, at 11:46 EST, an earthquake of m b = 5.0 occurred about 40 km east of Cleveland, Ohio, and about 17 km south of the Perry Nuclear Power Plant. The earthquake was felt over a broad area, including 11 states, the District of Columbia, and parts of Ontario, Canada, caused intensity VI-VII at distances of 15 km, and generated relatively high accelerations (0.18 g) of short duration at the Perry plant. Thirteen aftershocks were detected as of 15 April, with six occurring within the first 8 days. Two of the aftershocks were felt. Magnitudes for the aftershocks ranged from about 0.5 to 2.5. Focal depths for all of the earthquakes ranged from 2 to 6 km. Except for one small earthquake, all of the aftershocks occurred in a very tight cluster with a north-northeast orientation. Focal mechanisms of the aftershocks exhibit predominantly oblique right-slip motion on nearly vertical nodal planes oriented N15° to 45°E, with a nearly horizontal P axis north of east. Three deep waste disposal wells are currently operating within 15 km of the epicentral region and have been responsible for the injection of nearly 1.2 billion liters of fluid at pressures reaching 112 bars above ambient at a nominal depth of 1.8 km. Estimates of stress inferred from commercial hydrofracturing measurements suggest that the state of stress in northeastern Ohio is close to the theoretical threshold for failure along favorably oriented, preexisting fractures. This implies that effective stress conditions near the bottom of the two most active wells may be at or near the critical level for incipient failure. Two and, possibly, three earthquakes have occurred within less than 5 km from the wells since 1983. The relative distance to the main shock epicenter and its aftershocks (about 12 km), the lack of large numbers of small earthquakes typical of many induced sequences, the history of small to moderate earthquakes in the region prior to the initiation of injection, and the attenuation of the pressure field with distance from the injection wells, however, all argue for a “natural” origin for the 1986 earthquakes. In contrast, the proximity to failure conditions at the bottom of the well and the probable spatial association of at least one earthquake suggest that triggering by well activities cannot be precluded.