Open AccessThe scatter of time‐delays in shear‐wave splitting above small earthquakes
Author(s) -
Crampin Stuart,
Peacock Sheila,
Gao Yuan,
Chastin Sebastien
Publication year - 2004
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.2004.02040.x
Subject(s) - geology , seismology , shear (geology) , shear wave splitting , shear waves , seismic wave , geophysics , geodesy , petrology
SUMMARY Measurements of time‐delays in seismic shear‐wave splitting above small earthquakes typically display a scatter of often as much as ±80 per cent about the mean. Changes in the average time‐delay appear to be related to changes of stress, but applications of this potentially powerful tool have been handicapped by the previously inexplicable scatter in time‐delays above earthquakes. In contrast, measurements of shear‐wave time‐delays in controlled‐source exploration seismics are typically well controlled and display little scatter. Previous estimates of possible causes of scatter cannot produce sufficient variation specifically above earthquakes. Here we show that 90°‐flips in shear‐wave polarizations due to fluctuating high pore‐fluid pressures on seismically‐active fault planes are the most likely cause of the scatter.