Author(s): Sulistiyani; I Gusti Made Agung Nandaka; Nurudin; Anton Sulistio
Linked Author(s):
Keywords: Merapi; Early warning system; Lahar
Abstract: Merapi 2010 eruption was one of the great disaster phenomena. Approximately 130 million m³ pyroclastic material ejected, mostly entered Gendol River southeast part of the volcano. More than 50 lahar events were generated around Merapi during the early rainy season of 2011. The big amount of material made it bigger in magnitude and devastates the environment. Therefore, for mitigation purpose, lahar flows were monitored using non-contact detection instrumentation installed near the rivers. These devices were rain gauges, geophones (for real-time seismic amplitude measurement/RSAM and spectra calculation) and IP-based camera. This paper would present the response of these three parameters due to the lahar events. Lahar events occurred in 2011-2012 varied in duration, between 30 minutes to 4 hours. Due to the afternoon rainfalls occurrence, all lahar events were recognized from the monitoring stations between 15:00 — 17:00 WIB. Spectra of the lahar flow ranged from 8 — 14.8 Hz. The magnitude of the lahar events confirmed using visual data taken from the IP-camera. From the data, large lahar flow may be detected by RSAM unit exceeding 5000 counts for Gendol and Boyong River. These values can be set as the instrumental threshold for lahar early warning system. Information about these data spread to the society, community, and stakeholders by using Short Messaging System (SMS), Email and website.
Year: 2018