美国西部地区加卸载响应比的时空扫描及其地震趋势研究

The tempo-spatial scanning of Load/Unload response Ratio in Western America and study of its seismic tendency

加卸载响应比理论是近年来提出的地震预报新方法,在中国大陆地区的实际地震预测中取得了较好的效果。为了研究加卸载响应比理论是否适用于不同地质条件的地震,是否具有普适性,选择了典型的美国圣安德烈斯断层带及其周围地区的地震作为研究对象,计算分析了美国西部地区加卸载响应比的变化情况,并对该地区未来的地震趋势进行了研究。

The seismogenic process of an earthquake is very complicated. However, from the viewpoint of damage mechanics, the preparation process for an earthquake is the deformation and damage process of the seismogenic media. A new parameter called Load/ Unload Response Ratio （LURR） has been proposed as a measure of this process. In earthquake prediction LURR is typically defined as the ratio of released Benioff strain during loading cycles compared to that during unloading ones induced by the Earth tides. High LURR values （significantly larger than unity） indicate that a region is prepared for strong earthquakes. Retrospective examination of over hundred earthquake cases indicates that for more than 80% of the examined ones, a peak value of LURR will appear before the main shock. The peak value is much higher than 1. In previous years a series of successful intermediate-term predictions have been reported for strong earthquakes in China and other countries using the LURR parameter. The LURR theory is a new approach to earthquake prediction. Besides seismic energy and many other geophysical parameters concerning the seismogenic process such as Coda Q, ratio of velocities level of groundwater, crust deformation and tilt, geomagnetism parameters et al. could also be the response to define LURR. On the other hand LURR could be applied not only to natural earthquake prediction but also to forecasting other geological disaster such as reservoir-induced earthquakes, mine earthquake, rock-burst, landslide, volcano eruption, etc. Many strong earthquakes occurred in China＇s mainland have been predicted beforehand in term of LURR. But the geological setting in Western America is different from that in china＇s mainland. In order to investigate the application of LURR to different tectonic settings, the spatial scanning of LOAD/Unload Response Ration in Western America （30-50°N, 100-130°W） has been conducted. According to the results, we predicted that： （1） Earthquakes with magnitude around 5 will probably occur in the LURR anomaly regions showed in figure 4a, especially in the regions where the LURR is larger than 1.5 before July 31, 2005. （2） Earthquakes with magnitude around 5.5 will probably occur in the LURR anomaly regions showed in 4b, especially in the region where the LURR is larger than 1.5 before Dec. 31, 2005. （3） Earthquakes with magnitude around 6.5 will probably occur in the LURR anomaly regions showed in figure 4c, especially in the region where the LURR is larger than 1.5 before Dec. 31, 2006. Especially in the rectangle zone of 33-36°N, 115-118°W earthquakes with magnitude around 6.0 or even larger will probably occur before Dec. 31, 2005 or a little later.