Open AccessComment on ‘Systematic determination of earthquake rupture directivity and fault planes from analysis of long‐period P ‐wave spectra’ by L. M. Warren and P. M. Shearer
Author(s) -
Douglas A.
Publication year - 2007
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.2007.03370.x
Subject(s) - seismogram , seismology , geology , time domain , directivity , frequency domain , fault (geology) , range (aeronautics) , san andreas fault , earthquake rupture , mathematics , engineering , telecommunications , mathematical analysis , aerospace engineering , computer science , antenna (radio) , computer vision
SUMMARY Warren and Shearer describe a method of estimating the duration of P pulses radiated by earthquakes, on the assumption that the source is a unilateral fracture. The estimates are made in the frequency domain. The estimates obtained by Warren and Shearer for seven of the earthquakes are compared to durations estimated here in the time domain; the time‐domain measurements being made on broad‐band seismograms (∼0.1–4.0 Hz) derived by filtering from short‐period recordings. Overall, the time‐domain method indicates that the pulse duration of the earthquakes studied here range from 2.0 to 7.6 s, whereas the estimates from the results of Warren and Shearer range from 7.1 to 9.8 s. This suggests that the method of Warren and Shearer cannot resolve pulse lengths less than about 7 s. The suggestion is supported by the estimates of the duration of rupture—fault length/speed of rupture—implied by the results of Warren and Shearer. For, although the estimated fault‐length ranges from 0.8 km to over 40 km most rupture durations are around 8 s.