BPPTK Balai Penyelidikan dan Pengembangan Technology Kegunungapian

Yogyakarta, Indonesia

BPPTK Balai Penyelidikan dan Pengembangan Technology Kegunungapian

Yogyakarta, Indonesia
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Jousset P.,Bureau de Recherches Géologiques et Minières | Jousset P.,Helmholtz Center Potsdam | Budi-Santoso A.,BPPTK Balai Penyelidikan dan Pengembangan Technology Kegunungapian | Budi-Santoso A.,University of Savoy | And 6 more authors.
Journal of Volcanology and Geothermal Research | Year: 2013

The link between seismicity and degassing is investigated during the VEI 4 eruptions of Merapi volcano (Indonesia) in October and in early November 2010. Seismicity comprised a large number and variety of earthquakes including Volcano-Tectonic events, a sustained period of Long Period Seismicity (LPS), i.e., Long-Period events (LP), Very Long Period events (VLP) and tremor. LPS seismicity is ascribed to the excitation of fluid-filled cavity resonance and inertial displacement of fluids and magma. We investigate here LPS that occurred between 17 October and 4 November 2010 to obtain insights into the volcano eruption processes which preceded the paroxysmal phase of the eruption on 4-5 November. We proceed to the moment tensor inversion of a well-recorded large VLP event during the intrusion phase on 17 October 2010, i.e., before the first explosion on 26 October. By using two simplified models (crack and pipe), we find a shallow source for this VLP event at about 1km to the south of the summit and less than 1km below the surface. We analyze more than 90 LP events that occurred during the multi-phase eruption (29 October-4 November). We show that most of them have a dominant frequency in the range 0.2-4Hz. We could locate 48 of those LP events; at least 3 clusters of LP events occurred successively. We interpret these observations as generated by different fluid-filled containers in the summit area that were excited while magma rose. We also observe significant variations of the complex frequency during the course of the eruption. We discuss these changes in terms of a variable ratio of fluid to solid densities and/or by possible conduit geometry change and/or permeability of the conduit or the edifice and/or by resonance of different fluid-containers during the release of more than 0.4Tg of SO2 and large but unknown masses of other volcanic gases. Finally, we also discuss how the major explosions of the eruption were possibly triggered by passing waves resulting from regional tectonic earthquakes on 3 and 4 November. © 2013 Elsevier B.V.


Jousset P.,Bureau de Recherches Géologiques et Minières | Pallister J.,U.S. Geological Survey | Boichu M.,University of Cambridge | Buongiorno M.F.,Isituto Nazionale di Geofisica e Vulcanologia | And 14 more authors.
Journal of Volcanology and Geothermal Research | Year: 2012

Merapi volcano (Indonesia) is one of the most active and hazardous volcanoes in the world. It is known for frequent small to moderate eruptions, pyroclastic flows produced by lava dome collapse, and the large population settled on and around the flanks of the volcano that is at risk. Its usual behavior for the last decades abruptly changed in late October and early November 2010, when the volcano produced its largest and most explosive eruptions in more than a century, displacing at least a third of a million people, and claiming nearly 400 lives. Despite the challenges involved in forecasting this 'hundred year eruption', we show that the magnitude of precursory signals (seismicity, ground deformation, gas emissions) was proportional to the large size and intensity of the eruption. In addition and for the first time, near-real-time satellite radar imagery played an equal role with seismic, geodetic, and gas observations in monitoring eruptive activity during a major volcanic crisis. The Indonesian Center of Volcanology and Geological Hazard Mitigation (CVGHM) issued timely forecasts of the magnitude of the eruption phases, saving 10,000-20,000 lives. In addition to reporting on aspects of the crisis management, we report the first synthesis of scientific observations of the eruption. Our monitoring and petrologic data show that the 2010 eruption was fed by rapid ascent of magma from depths ranging from 5 to 30km. Magma reached the surface with variable gas content resulting in alternating explosive and rapid effusive eruptions, and released a total of ~0.44Tg of SO2. The eruptive behavior seems also related to the seismicity along a tectonic fault more than 40km from the volcano, highlighting both the complex stress pattern of the Merapi region of Java and the role of magmatic pressurization in activating regional faults. We suggest a dynamic triggering of the main explosions on 3 and 4 November by the passing seismic waves generated by regional earthquakes on these days. © 2012 Elsevier B.V.


Mei E.T.W.,University of Paris Pantheon Sorbonne | Mei E.T.W.,Gadjah Mada University | Lavigne F.,University of Paris Pantheon Sorbonne | Picquout A.,University of Paris Pantheon Sorbonne | And 6 more authors.
Journal of Volcanology and Geothermal Research | Year: 2013

The rapid onset and large magnitude of the 2010 eruption of Merapi posed significant challenges for evacuations and resulted in a peak number of almost 400,000 Internally Displaced Persons (IDPs). A pre-existing hazard map and an evacuation plan based on the relatively small magnitude of previous eruptions of the 20th century were utilized by emergency officials during the initial phase of the eruption (25 October-3 November, 2010). However, when the magnitude of the eruption increased greatly on 3-5 November 2010, the initial evacuation plan had to be abandoned as danger zones were expanded rapidly and the scale and pace of the evacuation increased dramatically. Fortunately, orders to evacuate were communicated quickly through a variety of communication methods and as a result many thousands of lives were saved. However, there were also problems that resulted from this rapid and larger-than-expected evacuation; and there were lessons learned that can improve future mass evacuations at Merapi and other volcanoes. We analyzed the results of 1969 questionnaires and conducted a series of interviews with community leaders and emergency officials. Results were compiled for periods both during and after the 2010 eruption. Our results show that: (1) trust in the Indonesian government and volcanologists was very high after the eruption; (2) multiple modes of communication were used to relay warnings and evacuation orders; (3) 50% to 70% of IDPs returned to the danger zone during the crisis despite evacuation orders; (4) preparation before the eruption was critical to the successes and included improvements to roads and education programs, (5) public education about hazards and evacuation protocols before the eruption was focused in the perceived highest danger zone where it was effective yet, confusion and loss of life in other areas demonstrated that education programs in all hazard zones are needed to prepare for larger-than-normal eruptions, and (6) improvements in registration of evacuees, in providing for livestock, and in activities and work programs in evacuation camps (as well as government restrictions and policy changes) are also needed to prevent evacuees from returning to their homes during the crisis period. © 2013 Elsevier B.V.

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