Using group velocities of seismic phases for regional event discrimination

We examined over the Israel Seismic Network (ISN) the seismogram envelopes vs. group velocity V = R/T, where R is the epicenter distance and T the travel time, and found out a persistent difference between quarry blasts and earthquakes. The data include 53 seismic events occurring in northern Israel with magnitudes of M-L = 1.0-2.6 and at distances of 15-310 km. Within the 1-4 km/s range we measured the velocity V-ms at which the envelope reaches its maximum for each ISN station. A simple linear discrimination function c = b + 0.33a, based on an empirical relationship between the V-ms and R: V-ms = a + b ln(R) provides effective separation between the regional earthquakes and explosions. These results are attributed to different excitation of regional surface waves from these two types of seismic events. (C) 1999 Elsevier Science B.V. All rights reserved.