Development of a modified envelope correlation method based on maximum-likelihood method and application to detecting and locating deep tectonic tremors in western Japan
Development of a modified envelope correlation method based on maximum-likelihood method and application to detecting and locating deep tectonic tremors in western Japan
复制标题
DOI：
10.1186/s40623-019-1022-x
复制
发表时间：
2019-04-11
影响因子：
3
通讯作者：
Ide, Satoshi
中科院分区：
文献类型：
--
作者：
Mizuno, Naoto;Ide, Satoshi
我们开发了一种改进的包络相关法定位深部构造地震，并将其应用于构建日本西部的地震目录。我们重新定义的包络互相关方法作为一个最大似然方法，通过使用互相关函数作为目标函数，然后加权组件的数据的误差方差的倒数。该方法还能够检测几乎同时发生的多个源，因为它们在我们的分析中表现为局部最大值。我们采用一个非线性函数，加权互相关函数（ACC）的平均值，定位深构造地震震源。我们的优化方法分两步进行。我们首先固定源深度，并使用网格搜索来找到局部ACC最大值，这是潜在的事件位置。然后，我们使用每个潜在事件位置作为初始值，并应用梯度方法来确定其震源位置。有时在5分钟的时间窗口内确定几个源位置。我们还使用合成波形进行了数值测试，以验证我们的震颤震源估计。我们将我们提出的方法应用于日本西部连续地震记录12.5年的时间，我们的新方法检测到的地震比包络相关方法与离群值控制多35%，由于在一个单一的时间窗口中检测到多个地震，并通过适当的加权方案提高了地震震源的准确性。我们估计的空间分辨率，这是定义为震源之间的距离，可以区分的位置方法，是类似于100公里。
We develop a modified envelope correlation method for locating deep tectonic tremors and apply it to construct a tremor catalog for western Japan. We redefine the envelope cross-correlation method as a maximum-likelihood method by using the cross-correlation functions as objective functions and then weighting components of the data by the inverse of the error variances. This method is also capable of detecting multiple sources that occur almost simultaneously because they appear as local maxima in our analysis. We employ a nonlinear function, the average of the weighted cross-correlation functions (ACC), to locate the deep tectonic tremor hypocenters. Our optimization method is performed in two steps. We first fix the source depth and use a grid search to find the local ACC maxima, which are the potential event locations. We then use each potential event location as an initial value and apply the gradient method to determine its hypocentral location. Several source locations are sometimes determined in a 5-min time window. We also perform a numerical test using synthetic waveforms to validate our tremor hypocenter estimations. We apply our proposed method to continuous seismograms in western Japan for 12.5-year period, with our new approach detecting 35% more tremors than the envelope correlation method with the outlier control owing to the detection of multiple tremors in a single time window and to the improved tremor hypocenter accuracy yielded by the appropriate weighting scheme. We estimate the spatial resolution, which is defined as the epicentral distance between sources that can be distinguished by the location method, to be similar to 100 km.