Wave Gradiometry for EarthScope Seismic and Strain Data

孟菲斯大学地震研究和信息中心首席研究员查尔斯·A·兰斯顿正在使用一种新的经验方法来分析地震波，称为波梯度法，用于研究地球镜可移动阵列记录的地震数据，并校准板块边界观测站(PBO)钻孔应变仪。来自远距离大地震的地震波的定量属性，如它们的速度、传播方位和幅度变化，正在通过计算地震台阵应变和旋转来确定。然后使用这些量的经验图首先识别地壳和地幔的异常区域，然后定量地确定北美大陆的大尺度地震速度结构。地震梯度测量技术允许确定地震波诱导的区域应变场作为已知的参考应变，以与来自PBO应变仪的观测应变进行比较。参考应变和观测应变通过矩阵数学和时间序列分析方法结合在一起，以产生对单个钻孔应变仪的精确校准。PBO应变仪的校准是使应变数据对板块边界观测站内活动地质过程的地震和构造研究有用的关键步骤。

Wave Gradiometry for EarthScope Seismic and Strain DataCharles A. Langston, Principal InvestigatorCenter for Earthquake Research and InformationUniversity of MemphisA new empirical method to analyze seismic waves, called wave gradiometry, is being used to study earthquake data recorded by the EarthScope Transportable Array and to calibrate Plate Boundary Observatory (PBO) borehole strain meters. Quantitative attributes of seismic waves from large, distant earthquakes such as their speed, azimuth of propagation, and amplitude changes are being determined by computing seismic array strains and rotations. Empirical maps of these quantities are then used to first identify anomalous regions of the crust and mantle and then to quantitatively determine large-scale seismic velocity structure of the North American continent. Seismic gradiometry techniques allow the determination of regional strain fields induced by the seismic waves to serve as a known reference strain to compare with observed strains from PBO strain meters. The reference and observed strains are being combined through matrix mathematics and time series analysis methods to produce precise calibration of individual borehole strain meters. Calibration of the PBO strain meters is an essential step in making the strain data useful for seismic and tectonic studies of active geological processes within the Plate Boundary Observatory.