大地震の断層モデルによる長周期地動変位・速度の予測

Abstract

Long-period ground displacements and velocities that would be observed at the time of threefuture possible large earthquakes in central Japan have been calculated from their reasonable faultmodels. The maximum horizontal displacements and velocities of long-period body waves withperiods longer than 10 sec for the so-called "Tokai earthquake" with thrust-type faulting could reach150-170 cm and 25-30 kine, respectively. These predicted values may vary to a factor of 2, depend-ing on the starting point of rupture on the presumed fault, the assumed rupture velocity and rise time.The corresponding values for two inland strike-slip earthquakes along the Atera and Atotsugawafaults may be estimated as 80 cm and 40 kine, respectively. These estimates do not involve surfacewaves nor converted body waves at the ground surface and interfaces in the crust, and hence shouldbe regarded as possible lower bounds.Possible sources of high frequency waves, which would be included in observed records but can-not be predicted from the above fault models, are discussed on the basis of more realistic hetero-geneous faults with non-uniform strengths.