A three-layered crustal model and corresponding Q structure for a central portion of northern Central America are derived using both travel-time and amplitude data of wide-angle reflections. Sources are very shallow earthquakes distributed along the Motagua fault in Guatemala and recorded at Tegucigalpa, Honduras.
Assuming a Pn velocity of 8.0 km/sec, P-wave velocities are derived as 5.79, 6.14, and 6.80 km/sec and layer thicknesses are 9.6, 14.6, and 13.2 km. The total crustal thickness is estimated at 37.4 km. Comparing observed and calculated amplitude ratios among three wide-angle reflections, we obtained Q values of 390 for the first layer and 260 for the third layer with an arbitrarily chosen Q of 500 for the second layer.
The crustal structure of northern Central America is similar to circum-Pacific continental structures such as those in southern Mexico, Peru, and Japan. This, coupled with the existence of a Paleozoic crystalline basement in the study area, strongly supports a continental origin for northern Central America.