Shallow earthquakes around the southwest boundary of Long Valley caldera, west of the Hilton Creek Fault, are characterized by lack of s-waves at regional seismic network stations to the northwest, north and northeast, and P-waves for these same station-event combinations are deficient in frequencies higher than about 2--3 Hz. Earthquakes east of the Hilton Creek fault and southeast of the caldera have normal P- and S-wave signatures at the same stations. These effects are explained by propagation through a magma chamber in the southcentral part of Long Valley caldera, at depth greater then 7--8 km.