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

[SSS06-10] Multi-array experiment of seismic monitoring at Merapi volcano using low-cost seismometers at sub-optimal distances

*Theodorus Permana¹、Wolfgang Kohl²、Ade Anggraini¹、Herlan Darmawan¹、Wiwit Suryanto¹ (1.Seismology, Volcanology, and Disaster Hazards Research Group, Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Gadjah Mada、2.gempa GmbH)

キーワード：seismic array, volcano seismology, volcano monitoring, Merapi, low-cost instrument, volcanic earthquakes

In a time of rapid rise in technology and techniques for seismic monitoring, particularly at volcanoes, cost and technical issues remain the limiting factors for the application of these new instruments and techniques in many places around the world. Fortunately, several high-quality seismic instruments are now available at a lower cost, making them accessible to more parties with limited resources. Around Merapi volcano in Indonesia, we installed two small-aperture arrays of low-cost instruments, each consisting of five Raspberry Shake and Boom (RS&BOOM) vertical seismic and infrasound sensors to study their reliability in discriminating between tectonic and volcanic seismic events. Due to technical and logistic reasons, the arrays were installed at distances of 11 and 17 km from the active lava dome, which may be considered suboptimal for detailed monitoring of volcano seismicity. Despite this limitation, we confirm that some seismic signals from surface and subsurface events can be captured by the arrays. Considering the complexity of volcano-seismic signals and the difficulties in detecting and locating them using conventional arrival time-based methods, we develop and apply a detection and characterization approach based on signal similarity and array analysis. Both arrays are available since November 2024, during which volcanic earthquakes of volcanotectonic and multiphase/hybrid types are abundant, as well as surface rockfall events. Our detected events show an apparent consistency compared with the official event counts and observations, despite a much smaller number of events due to the arrays only capturing larger-magnitude events. We further investigate the reliability and accuracy of our suboptimal arrays in monitoring volcanic seismicity, by examining the effect of station coverage, sampling frequency, and source depth. Despite significant limitations, our experiment shows useful insight and promising future for low-cost seismic monitoring, particularly in establishing a local network of instruments in close proximity of the volcano for a proper and detailed observation of seismicity which may help in eruption prediction and hazard reduction efforts.