Open AccessThe ‘tsunami earthquake’ of 1932 June 22 in Manzanillo, Mexico: seismological study and tsunami simulations
Author(s) -
Okal Emile A.,
Borrero José C.
Publication year - 2011
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.2011.05199.x
Subject(s) - seismology , aftershock , geology , tsunami earthquake , seismic moment , foreshock , slowness , shock (circulatory) , fault (geology) , geodesy , medicine
SUMMARY We conduct a detailed seismological study of the large Colima, Mexico earthquake of 1932 June 3 and of its aftershocks of June 18 and 22. The latter (Event III) generated a tsunami more devastating than that of the main shock despite much smaller seismic magnitudes, thus qualifying as a so‐called ‘tsunami earthquake’. Relocation based on published arrival times shows that Event III took place up‐dip of the main shock. The analysis of the spectral amplitude of mantle surface waves yields low‐frequency moments of 24, 5.2 and 4 times 10 27 dyn cm, respectively, with Event III featuring a moment growing with period, which expresses the source slowness characteristic of ‘tsunami earthquakes’. This is confirmed by a deficient energy‐to‐moment ratio, as derived from high‐frequency P waves recorded at Pasadena. Near‐field hydrodynamic simulations show that the effects of the main shock's tsunami are well modelled by a standard seismic source, whereas the stronger tsunami from Event III can be modelled by rupture along a splay fault in a mechanically deficient material. All our results then fit the model for ‘tsunami earthquake’ aftershocks proposed for the Kuril Islands by Fukao in 1979.