Open AccessSTUDY OF A SERIES OF JAPANESE EARTHQUAKES
Author(s) -
Lapwood E. R.
Publication year - 1955
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.1955.tb06559.x
Subject(s) - epicenter , series (stratigraphy) , geodesy , geology , discontinuity (linguistics) , seismology , shock (circulatory) , azimuth , position (finance) , mathematics , geometry , mathematical analysis , medicine , paleontology , finance , economics
Summary The I.S.S. for 1935 records a series of seven earthquakes with the same epicentre off the east coast of Japan. This series, in which the I.S.S. identifies many arrivals as P * or S *, was examined in the hope of estimating velocities of P * and S *. Straight lines fitted to first arrivals at stations of azimuth 180° to 270° gave the local velocity of P as 7.77 ± 0.04 km/sec. Epicentre and origin‐time were then redetermined for each shock, and revised times of arrival plotted against revised epicentral distances. The following conclusions were reached:No series of arrivals could be identified as P * or S *. The redetermined epicentres show an approximately linear arrangement. The uncertainty in position of each epicentre is comparable with the distance between successive epicentres, and may be due to the spatial extent of the focus. There is a clustering of points between Δ=4° and Δ=9° about a line which would represent a pulse travelling with the velocity of S but 15.8 sec later than S. The delay may be used to obtain an estimate of the depth of the Mohorovičié discontinuity.