Teleseismic and earth noise monitoring with the Block-Moore quartz accelerometer

A study has been made of some recent data recorded through the seismic channel of a broad-band vertical quartz accelerometer operating near San Diego, California. Such a study has provided information concerning instrument capabilities for detection of surface waves from small teleseisms and Earth noise levels, including temporal variations. The data suggest that detection thresholds of the same order as those of the high-gain long-period installation at Ogdensburg are attainable at a surface site with the quartz instrument. Indications are that an approximate 10 db gain in surface wave detection would in general provide high probability of detection (c. 0.85) of mb = 4 earthquakes at distances of ∼40°. In addition, results suggest that noise levels in the range 5–200s recorded at this site with the accelerometer are comparable to those obtained at other surface sites, and somewhat higher than those obtained at depth for periods longer than about 30s. A study of number of events recorded has demonstrated that nearly half (∼47 per cent) of all events reported by the NOAA PDE program were detected.