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A fast and simple diagnostic method for identifying tsunamigenic earthquakes
Author(s) -
Shapiro N. M.,
Singh S. K.,
Pacheco J.
Publication year - 1998
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/1998gl900015
Subject(s) - seismogram , seismology , geology , trench , seismometer , subduction , moment magnitude scale , magnitude (astronomy) , seismic moment , tsunami earthquake , tectonics , fault (geology) , chemistry , physics , geometry , mathematics , organic chemistry , layer (electronics) , astronomy , scaling
An analysis of regional broadband seismograms of moderate and large subduction‐zone earthquakes in Mexico shows that earthquakes which occur near the trench are abnormally depleted in high‐frequency radiation. This observation leads to a simple and fast method to assess regional tsunami potential from earthquakes which occur along the Pacific coast of Mexico. A significant advantage of the method is that a single broadband seismograph is sufficient for the purpose. The method is based on the ratio of the total energy to the high‐ frequency energy (between 1 and 5 Hz), ER , computed from the seismograms. For earthquakes with the same seismic moment, ER is an order of magnitude greater for a source area near the trench as compared to those near the coast. The same seismograms are used to compute energy magnitude, M E , which is tied to the moment magnitude, M W . A regional tsunami may be expected along the coast if M E ≥ 6.5 and ER corresponds to a source near the trench. If, however, ER corresponds to a near‐coast source, then M E may have to be greater than about 7.3 for a tsunami of similar size to occur along the coast. The method holds promise for a fast regional tsunami warning in many Pacific basin countries which lack an adequate seismic network.