Influence of Tidal Forces on the Triggering of Seismic Events
Influence of Tidal Forces on the Triggering of Seismic Events
复制标题
潮汐力对地震事件触发的影响
DOI：
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发表时间：
2018
影响因子：
2
通讯作者：
E. Grafarend
中科院分区：
文献类型：
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作者：
P. Varga;E. Grafarend
潮汐应力产生于任何三维物体中，受到旋转行星或卫星的外部不均匀重力场的影响。本文从体潮对地震活动影响的角度，讨论了体潮在固体地球内部引起的应力，作为一种特殊情况。月球和太阳的地震触发效应通常是通过潮汐变化和地震活动时间分布的统计比较，或者使用地震倾向结构中物理过程的数学或实验模型来研究的。在这项研究中，计算了PREM的日月应力张量的大小，其分量沿着地球球面的纬度以及地球内部（直到地核-地幔边界）（Dziewonski和安德森，物理地球行星间25（4）：297-356，1981）。计算结果表明，应力随深度的增加而增加，在900-1500 km深度处，应力值约为kPa，远低于深震区。在地震能量聚集的绝大部分深度（约50 km），日月源应力仅为（0.0-1.0）·103 Pa。尽管这些值远小于地震应力降（1-30 MPa）（Kanamori in Annu Rev Earth Planet Sci 22：207-237，1994），但这并不排除潮汐力对地震事件爆发的影响的可能性。由于潮汐势及其导数与坐标有关，从地表到CMB，纬向、正方形和扇形潮汐有不同的分布，因此日月应力对每个地震事件的影响程度不可能相同。固体潮对地震发生的影响，首先与平行于地球表面作用的应力分量有关。负荷潮汐的影响仅限于负荷区及其附近。
Tidal stresses are generated in any three-dimensional body influenced by an external inhomogeneous gravity field of rotating planets or moons. In this paper, as a special case, stresses caused within the solid Earth by the body tides are discussed from viewpoint of their influence on seismic activity. The earthquake triggering effects of the Moon and Sun are usually investigated by statistical comparison of tidal variations and temporal distribution of earthquake activity, or with the use of mathematical or experimental modelling of physical processes in earthquake prone structures. In this study, the magnitude of the lunisolar stress tensor in terms of its components along the latitude of the spherical surface of the Earth as well as inside the Earth (up to the core-mantle boundary) were calculated for the PREM (Dziewonski and Anderson in Phys Earth Planet Inter 25(4):297–356, 1981). Results of calculations prove that stress increases as a function of depth reaching a value around some kPa at the depth of 900–1500 km, well below the zone of deep earthquakes. At the depth of the overwhelming part of seismic energy accumulation (around 50 km) the stresses of lunisolar origin are only (0.0–1.0)·103 Pa. Despite the fact that these values are much smaller than the earthquake stress drops (1–30 MPa) (Kanamori in Annu Rev Earth Planet Sci 22:207–237, 1994) this does not exclude the possibility of an impact of tidal forces on outbreak of seismic events. Since the tidal potential and its derivatives are coordinate dependent and the zonal, tesseral and sectorial tides have different distributions from the surface down to the CMB, the lunisolar stress cannot influence the break-out of every seismological event in the same degree. The influencing lunisolar effect of the solid earth tides on earthquake occurrences is connected first of all with stress components acting parallel to the surface of the Earth. The influence of load tides is limited to the loaded area and its immediate vicinity.