Source location of volcanic earthquakes and subsurface characterization using fiber-optic cable and distributed acoustic sensing system

We present one of the first studies on source location determination for volcanic earthquakes and characterization of volcanic subsurfaces using data from a distributed acoustic sensing (DAS) system. Using the arrival time difference estimated from well-correlated waveforms and a dense spatial distribution of seismic amplitudes recorded along the fiber-optic cable, we determine the hypocenters of volcanic earthquakes recorded at Azuma volcano, Japan. The sources are located at a shallow depth beneath active volcanic areas with a range of approximately 1 km. Spatial distribution of the site amplification factors determined from coda waves of regional tectonic earthquakes are well correlated with old lava flow distributions and volcano topography. Since DAS observation can be performed remotely and buried fiber-optic cables are not damaged by volcanic ash or bombs during eruptions, this new observation system is suitable for monitoring of volcanoes without risk of system damage and for evaluating volcanic structures.

Automated summary

This study presents a novel method for source location determination of volcanic earthquakes and characterization of volcanic subsurfaces using a distributed acoustic sensing (DAS) system. By analyzing well-correlated waveforms and seismic amplitudes recorded along a fiber-optic cable, the hypocenters of volcanic earthquakes at Azuma volcano, Japan were successfully determined, showing a shallow depth beneath active volcanic areas. The spatial distribution of site amplification factors from coda waves of regional tectonic earthquakes is correlated with old lava flow distributions and volcano topography.