HR: 0800h
AN: V21C-0621    [Abstracts]
TI: Volcanic Tremor Location During The 2004 Lava Effusion At Mt. Etna, Italy, Based On Amplitude Decay
AU: * Langer, H K
EM: langer@ct.ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania, Piazza Roma, 2, Catania, CT 95123 Italy
AU: Di Grazia, G
EM: digrazia@ct.ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania, Piazza Roma, 2, Catania, CT 95123 Italy
AU: Falsaperla, S
EM: falsaperla@ct.ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania, Piazza Roma, 2, Catania, CT 95123 Italy
AB: Tremor is commonly addressed to as the RMS-amplitude of the seismic signal measured over a time window within a defined frequency band. On basaltic volcanoes like Mt. Etna, volcanic tremor is recorded as a persistent signal with no clearly identifiable seismic phases. Therefore, the location of its sources with traditional event location methods fails. Following the efforts of the Istituto Nazionale di Geofisica e Vulcanologia (INGV) to increase the number of seismic stations along with data quality and the reliability of data acquisition, we tackle the location problem using the spatial tremor amplitude distribution. Estimates of source location can be obtained using a simplified attenuation law. In this study, we propose a robust method to monitor the migration of tremor sources at Mt. Etna from January 2004 on, including the last eruption, which started on 7 September, 2004 and ended on 8 March, 2005. We estimate the location uncertainty carrying out random experiments with respect to the station configuration. We also assess the reliability of our location method applying it to local seismic events for which conventional locations were available, and comparing the results. The sources identified from the tremor amplitude distribution cannot be easily related to the theatre of the eruption. On the other hand, from the composition of the erupted magma, we infer that this last volcano unrest is due to a superficial phenomenon, with weak or no links to the deep internal dynamics of the magma feeder.
DE: 7280 Volcano seismology (8419)
DE: 8419 Volcano monitoring (7280)
DE: 8425 Effusive volcanism
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005