Magnitude-corner frequency distribution of explosion earthquakes: a case study of Anak Krakatau Volcano, Sunda Strait

We investigated the distribution between the magnitude and corner frequency of explosion earthquakes at the Anak Krakatau volcano during June - July 2014. We analyzed 100 explosion waveforms recorded at the KRA3 and KRA4 seismic stations located approximately 0.55 km and 3.84 km away from the active crater, respectively. We observed a relationship between the moment magnitude and the corner frequency of the explosion earthquake distribution. The result shows that the moment magnitude is inversely proportional to the corner frequency in a logarithmic scale using the full waveform of explosion earthquakes. The distribution equation of full waveform (0-20s) at KRA3 and KRA4 as follows; f c = −2.72145 log( M w ) + 7.99523, and f c = −1.13971 log( M w ) + 5.97855 respectively. The magnitude range is approximately 1.5–3 Mw. Meanwhile, the corner frequency range is about 4-8 Hz. Our result shows a similar distribution to those in the tectonic earthquake and volcano studies at different locations which is the magnitude is inversely proportional to the corner frequency. We also observed the relation between seismic moment and corner frequency which shows that the seismic moment is inversely proportional to the corner frequency with the range of seismic moment is about 10 13 -10 15 N.m. Meanwhile, the stress drop is proportional to the corner frequency with the range of stress drop is about 10 0 and 10 3 bar. Our results are similar to those of other studies. These parameters show the basic statistical properties of volcanic eruptions. This study is important for understanding the dynamics of volcanic eruptions at the Anak Krakatau volcano.