Evidence of low Q below Popocatepetl volcano, and its implication to seismic hazard in Mexico City

Abstract

Seismograms recorded in Mexico City reveal that the amplitudes of seismic waves whose wavepaths pass below Popocatepetl, presently an volcano, before reaching the city are diminished by a factor of about one-third at frequencies greater than 1 Hz as compared to those which do not cross the volcano. The high attenuation of seismic waves below the volcano may be attributed to the presence of magma and partial melting of rocks. Q of shear waves below the volcano is roughly estimated as 60. A consequence of the large attenuation of high-frequency seismic waves is a decrease in the seismic hazard of low-rise buildings in Mexico City from intraplate earthquakes whose wavepaths cross the volcano.