Inter-event time statistics of earthquakes as a gauge of volcano activity

TL;DR

This study analyzes the inter-event time distribution of volcanic earthquakes, revealing stage-dependent power-law exponents that could serve as indicators of imminent volcanic activity.

Contribution

It identifies stage-specific power-law exponents in volcanic earthquake inter-event times, linking seismic patterns to volcanic activity stages.

Findings

Steady seismicity shows exponents 0.6-0.7

Burst periods have exponents around 1.3

Preburst phase exhibits an exponent of about 1.0

Abstract

The probability distribution of inter-event time (IET) between two consecutive earthquakes is a measure for the uncertainty in the occurrence time of earthquakes in a region of interest. It is well known that the IET distribution for regular earthquakes is commonly characterized by a power law with the exponent of 0.3. However, less is known about other classes of earthquakes, such as volcanic earthquakes, which do not manifest mainshock-aftershocks sequences. Since volcanic earthquakes are caused by the movement of magmas, their IET distribution may be closely related to the volcanic activities and therefore of particular interest. Nevertheless, the general form of IET distribution for volcanic earthquakes and its dependence on volcanic activity are still unknown. Here we show that the power-law exponent characterizing the IET distribution exhibits a few common values depending on the stage of volcanic activity. Volcanoes with steady seismicity exhibit the lowest exponent ranging from 0.6 to 0.7. During the burst period, when the earthquake rate is highest, the exponent reaches its peak at approximately 1.3. In the preburst phase, the exponent takes on the intermediate value of 1.0. These values are common to several different volcanoes. Since the preburst phase is characterized by the distinct exponent value, it may serve as an indicator of imminent volcanic activity that is accompanied by a surge in seismic events.