The use of regional hydrophone datasets for statistical studies of mid‐ocean ridge earthquake populations

Seismically generated tertiary (T‐) waves can be used to detect and locate the shallow hypocenter earthquakes associated with mid‐ocean ridge spreading centers and oceanic transforms. During the last several years, regional seismic catalogs, which contain estimates of T‐wave source regions, origin times and acoustic source levels, have been generated from continuous hydroacoustic monitoring along the northern Mid‐Atlantic Ridge and equatorial East Pacific Rise. As the mechanics of T‐wave generation remain poorly understood, critics of these datasets have questioned the correlation between T‐wave source regions and seismic epicenters, as well as the usefulness of acoustic source level as a proxy for earthquake size. Recent analyses, however, suggest that these data provide a reasonably complete record of seismicity within the mid‐ocean ridge environment, yielding significant improvements in location accuracy and catalog completeness level, relative to global seismic catalogs. Most importantly, it appears that many fundamental and well‐established properties of seismic distributions can be studied using T‐wave catalogs, including the modified Omori decay law of aftershocks, a power‐law size frequency distribution (Gutenberg–Richter law), a fractal time‐clustering behavior (1/f noise) and fractal spatial distribution of epicenters. These observations show that T‐wave derived earthquake catalogs can be used for quantitative seismo‐tectonic studies in the ridge setting.