Phased Array Analysis Incorporating the Continuous Wavelet Transform

Session: Explosion Seismology Advances
Type: Oral
Date: 4/29/2020
Time: 02:45 PM
Room: 240
Description: 

Non-linear block thresholding of the continuous wavelet transform (CWT) of 2D phased array signals offer high time-resolution solutions for analyzing seismograms of local and regional seismic events. An initial denoising step on an array ensemble reveals those regions of the scale-time plane that contain high signal-to-noise arrivals. Individual seismic phase arrivals in ensemble, denoised seismograms can be partitioned using scale-time gating where CWT wave packets of an individual seismic phase on the scale-time plane for a reference array element are time-correlated with all other elements to find an optimum time shift for the phase across all elements. The seismic phase is then clipped out of the CWT of each array element using this optimal time shift for further analysis. The seismogram can be separated into component seismic waves for a detailed view of wave characteristics such as slowness and arrival azimuth using conventional frequency-wavenumber methods. However, the process can be taken further by using the CWT of each phase to construct high time-resolution signal beams over CWT scale. Local earthquake and explosion data from the 2016 IRIS Wavefields community experiment are used to demonstrate these techniques in separating surface wave modes and body waves. High resolution CWT processing in the 1 to 3 Hz band reveals horizontal Rayleigh refraction and multipathing. Phase velocity measurements of component regional phases along with well-log data are used to construct a 1D velocity model under the array.

Presenting Author: Charles A. Langston

Authors