[S-SS06] New trends in data acquisition, analysis and interpretation of seismicity

[SSS06-07] Inter-event time statistics for volcanic earthquakes

★Invited Papers

*Takahiro Hatano¹, Kundu Sumanta^1,2, Yosuke Aoki³, Anca Opris¹ (1.Department of Earth and Space Science, Osaka University, 2.Scuola Internazionale Superiore di Studi Avanzati (SISSA), 3.Earthquake Research Institute, The University of Tokyo)

Keywords:Inter-event time, volcanic earthquakes

The probability distribution of inter-event time (IET) between two consecutive earthquakes characterizes the uncertainty in the occurrence time of earthquakes in a region of interest, and therefore has been extensively studied for regular earthquakes. However, less is known about other classes of earthquakes. For instance, volcanic earthquakes do not exhibit mainshock-aftershocks sequence and therefore may exhibit different IET statistics.

Here we analyze the IET distributions for several volcanoes and find that the IET distribution develops a power-law tail with the exponent much larger than that for regular earthquakes. More importantly, the exponent shows a general dependence on the stage of volcanic activity characterized by a few common values. Volcanoes with steady seismicity exhibit the lowest exponent, ranging from 0.6 to 0.7, while it is the largest (approximately 1.3) during the burst period with the highest rate of volcanic earthquakes. Interestingly, the preburst phase may be characterized by the intermediate value, 1.0. This is significantly larger than that for the steady activity, and therefore could be interpreted as a precursor of eruption accompanied with a burst of earthquakes. However, a counterexample is the Kilauea case, in which the exponent in the preburst period (2012-2017) does not significantly change from the steady period.