Seismic moment rate and recurrence interval of small-size earthquakes from a 3-D perspective

Repeating postseismic event sequences associated with featured variations
of the moment magnitude spectrum and recurrence interval have been
fruitfully studied by previous researchers. However, similar features of
recorded regular earthquakes are much less frequently observed due to
their lower event recurrence frequencies and the range or accuracy limits
of the employed observation systems. Based on rapidly increasing catalogs
of earthquakes with high-resolution epicenter locations made possible in
recent decades and combined with three-dimensional (3-D) numerical
calculation techniques, we employ a 3-D seismic density sphere method that
recognizes the vertical depth as a similar dimension as the horizontal
distance to more quantitatively investigate the seismic moment-recurrence
interval (M0-SI) relationship in known seismically active regions in
Japan. A subset of 49 seismogenic zones of the 1.8 million events
collected in fifteen years show that the logarithm of the seismic interval
for regular events is likely proportional to the logarithm of the seismic
moment. The recorded M5+ earthquakes preferentially recur at a plate
convergent margin, where larger seismic moment rates are calculated. We
therefore present a scaling law for regular earthquakes between the
seismic moment and the seismic interval in which the scale coefficient is
determined by the seismic moment rate which is possibly related to the
dimensions of the fault slip behavior and similar to an M0-SI relationship
of the detected the pre- and postseismic repeating earthquake sequence.
The seismic moment rate influences the earthquake recurrence frequency,
which varies by area and depth.