Seismic Energy: Measurement, Mechanism Dependence, and Scaling

本项目拟对地震能量的测量、机理依赖和标度进行研究。地震能量的估计存在较大的潜在误差，同一次地震的不同估计通常相差10倍或更多，不同研究报告的地震能量的标度特性和震源机制依赖性是相互矛盾的。有的研究发现地震应力降（用地震能量除以地震矩计算）随地震大小而变化，有的研究发现没有变化。一些研究发现地震应力降的系统变化与震源机制有关，而另一些研究发现地震应力降与震源机制无关。几项研究表明，远震对地震能量的估计比近震源估计低一个数量级，但这种差异的来源尚未确定和纠正。地震能量很难估计，因为它是对震源强度的宽频测量，因此必须考虑并校正波的传播效应和震源在宽频率范围内的激励。在提出的研究中，研究将利用现代宽带数字数据来解决地震能量估计的差异。这些改进的估计将用于测试可能的尺度和机制依赖，并探索它们对地震过程的影响。

This project proposes to study the measurement, mechanism dependence, and scaling of seismic energy. Estimates of the seismic energy have large potential errors, with different estimates for the same earthquake commonly varying by a factor of 10 or more, and the scaling properties and focal mechanism dependence of seismic energy reported by different studies are contradictory. Some studies find that the earthquake stress drop (calculated by dividing seismic energy by the seismic moment) varies with earthquake size, while other studies find no variation. Some studies find a systematic variation of earthquake stress drop with focal mechanism, while others find no mechanism dependence. Several studies have suggested that teleseismic estimates of seismic energy are about an order of magnitude lower than near-source estimates, yet the source of this discrepancy has not been identified and corrected. Seismic energy is difficult to estimate because it is a broadband measure of the strength of the earthquake source and hence one must account and correct for both wave propagation effects and source excitation over a wide frequency range. In the proposed study, the research will take advantage of modern broadband digital data to resolve discrepancies in estimates of the seismic energy. These improved estimates will be used to test for possible scaling and mechanism dependence and explore their implications for the earthquake process.