ANALYSIS OF THE ATTENUATION OF STRONG GROUND MOTION ON THE ISLAND OF HAWAII

We develop a horizontal peak ground acceleration (PGA) predictive equa tion for the island of Hawaii by applying the Joyner and Boore (1993, 1994) two-stage regression method to a data set that consists of 51 PG A from 22 events. Magnitudes vary from 4.0 to 7.2, and event depths va ry from 4 to 14 km, The resulting equation is log(10)PGA = 0.518 + 0.3 87 (M - 6) - log(10)r - 0.00256r + 0.335S, where PGA is measured in un its of g, M is magnitude, r = (d(2) + 11.29(2))(1/2), and S is 0 for l ava sites and 1 at ash sites. The distance parameter d is the closest distance from the recording site to the surface projection of the faul t rupture area and varies from 0 to 88 km for the Hawaii PGA data set. We find that the attenuation of high-frequency strong ground motion i s significantly greater than a previous relationship used for the isla nd of Hawaii, The ash site coefficient S, which represents acceleromet er sites with shear-wave velocities that vary from 60 to 200 m/sec, is generally larger than the soil site coefficients in other attenuation relationships.