Cascadia Tremor Located Near Plate Interface Constrained by S Minus P Wave Times
Cascadia Tremor Located Near Plate Interface Constrained by S Minus P Wave Times
复制标题
卡斯卡迪亚震颤位于板块界面附近，受 S 负 P 波时间约束
作者：
M. La Rocca;K. Creager;D. Galluzzo;S. Malone;J. Vidale;J. Sweet;A. Wech
非火山地震很难定位，因为它不会产生可通过地震网络识别的脉冲相位。识别特定相位的另一种方法是测量 S 波和 P 波之间的滞后。我们对垂直和水平地震图进行交叉关联，以揭示两者共有的信号，但水平相对于垂直有延迟。这种滞后相关性代表垂直压缩波和水平剪切波之间的时间间隔。对该间隔的测量结合定位技术，可解析±2公里范围内的震源深度。对于最近的卡斯卡迪亚地震，震源位于俯冲板片界面附近或之上。强相关性和稳定的 S-P 时间差意味着震颤由重复源的辐射组成。
Nonvolcanic tremor is difficult to locate because it does not produce impulsive phases identifiable across a seismic network. An alternative approach to identifying specific phases is to measure the lag between the S and P waves. We cross-correlate vertical and horizontal seismograms to reveal signals common to both, but with the horizontal delayed with respect to the vertical. This lagged correlation represents the time interval between vertical compressional waves and horizontal shear waves. Measurements of this interval, combined with location techniques, resolve the depth of tremor sources within ±2 kilometers. For recent Cascadia tremor, the sources locate near or on the subducting slab interface. Strong correlations and steady S-P time differences imply that tremor consists of radiation from repeating sources.