Spatial and Temporal Distributions of Microearthquake Activity

Recently, telemetered microearthquake observation networks have been developed, and data acquisition and processing procedures have been automated in many networks, including automatic hypocenter determinations by using computers. As a result the detection capability and the accuracy of hypocenter determination of microearthquakes have been tremendously improved, which made a great advance in detailed microearthquake studies. We present a brief review on recent studies of seismicity based on microearthquake observations, focusing on spatial and temporal distributions of microearthquakes and their related problems.