| Title | Multichannel alignment of s-waves |
|
|
| Author | Bostock, M G; Plourde, A P ; Drolet, D; Littel, G |
| Source | Bulletin of the Seismological Society of America vol. 112, no. 1, 2022 p. 133-142, https://doi.org/10.1785/0120210076 |
| Image |  |
| Year | 2022 |
| Alt Series | Natural Resources Canada, Contribution Series 20210130 |
| Publisher | Seismological Society of America |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Province | British Columbia |
| NTS | 92B/02; 92B/03; 92B/06; 92B/07; 92B/10; 92B/11 |
| Lat/Long WENS | -123.5000 -122.5000 48.7500 48.0000 |
| Subjects | tectonics; mathematical and computational geology; p waves; s waves; seismic waves; earthquakes |
| Illustrations | schematic diagrams; location maps; seismic profiles; seismic sections; plots |
| Released | 2021 09 14 |
| Abstract | High resolution earthquake locations and structural inversions using body waves rely on precise delay-time measurements. Subsample accuracy can be realized for P-waves using multichannel cross
correlation (MCCC), as developed by VanDecar and Crosson (1990), that exploits redundancy in pair-wise cross-correlations to determine delays between similar waveforms in studies of mantle structure using teleseismic sources
(common-source/multiple-stations) and regional studies of structure and seismicity (common-station/multiple sources). For regional S-waves, alignment is complicated by the additional degree of freedom in waveform polarity that is expressed for
sources with different moment tensors. Here we recast MCCC within a principal component framework and demonstrate the equivalence between maximizing waveform correlation and minimization of various singular-value-based objective functions for
P-waves. The singular-value framework is more general and leads naturally to an MCCC linear system for S-waves that possesses an order of magnitude greater redundancy than that for P-waves. Robust L1 solution of the system provides an effective means
of mitigating outliers at the expense of subsample precision. Residual time shifts associated with higher-order singular vectors are employed in an iterative adaptive alignment that achieves subsample resolution. We demonstrate application of the
approach on a seismicity cluster within the northern Cascadia crustal fore-arc. |
| Summary | (Plain Language Summary, not published)
Precise estimates of earthquake locations help us understand both earthquake hazard and the geological structure of earth's crust. To achieve precise
locations, we often assume that nearby earthquakes produce highly similar waveforms. However, while this is true for compressional (P) waves, it is not necessarily true for shear (S) waves. This paper presents a new method for processing S waves from
groups of nearby earthquakes in order to estimate precise locations. The method is tested on a group of over 100 earthquakes from southwestern British Columbia. |
| GEOSCAN ID | 328446 |
|
|