«The 2010 explosive eruption of Java’s Merapi volcano - a ’100-year’ event M. Surono, Philippe Jousset, John Pallister, Marie Boichu, Maria ...»
The 2010 explosive eruption of Java’s Merapi volcano - a
M. Surono, Philippe Jousset, John Pallister, Marie Boichu, Maria Fabrizia
Buongiorno, Agus Budisantoso, Fidel Costa Rodriguez, Supriyiat Andreastuti,
Fred Prata, David Schneider, et al.
To cite this version:
M. Surono, Philippe Jousset, John Pallister, Marie Boichu, Maria Fabrizia Buongiorno,
et al.. The 2010 explosive eruption of Java’s Merapi volcano - a ’100-year’ event.
Journal of Volcanology and Geothermal Research, Elsevier, 2012, 241-242, pp.121-135.
10.1016/j.jvolgeores.2012.06.018. insu-00723412 HAL Id: insu-00723412 https://hal-insu.archives-ouvertes.fr/insu-00723412 Submitted on 10 Aug 2012 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destin´e au d´pˆt et ` la diﬀusion de documents e eo a entiﬁc research documents, whether they are pub- scientiﬁques de niveau recherche, publi´s ou non, e lished or not. The documents may come from ´manant des ´tablissements d’enseignement et de e e teaching and research institutions in France or recherche fran¸ais ou ´trangers, des laboratoires c e abroad, or from public or private research centers. publics ou priv´s.
e The 2010 explosive eruption of Java's Merapi volcano – a ‘100year’ event Suronoa1 Philippe Joussetbc2 John Pallisterd3 Marie Boichue45 M. Fabrizia Buongiornof6 Agus Budisantosogh7 Fidel Costai Supriyati Andreastutia Fred Prataj8 David Schneiderk9 Lieven Clarissel10 Hanik Humaidag6 Sri Sumartig6 Christian Bignamf5 Julie Griswoldd3 Simon Carnm11 Clive Oppenheimereno412 Franck Lavignep a Center of Volcanology and Geological Hazard Mitigation, Jalan Diponegoro 57, 40122 Bandung, Indonesia b BRGM, RIS, 3 Avenue Claude Guillemin, BP36009, 45060 Orléans Cedex 2, France c Now at GFZ German Research Center in Geosciences, Telegrafenberg, 14473 Potsdam, Germany d U.S. Geological Survey, Cascades Volcano Observatory, 1300 SE Cardinal Court, Vancouver, WA 98604, USA e The University of Cambridge, Department of Geography, Downing Place, Cambridge CB23EN, United Kingdom f Isituto Nazionale di Geofisica e Vulcanolgia, Via di Vigna Murata 605, 00143 Rome, Italy g BPPTK (Balai Penyelidikan dan Pengembangan Teknologi Kegunungapian), Jalan Cendana 15, Yogyakarta 55166, Indonesia h ISTerre, CNRS, Université de Savoie, 73376 Le Bourget du Lac cedex, France i Earth Observatory of Singapore, Nanyang Technological University N2-01a-10, Singapore 639798 j Climate and Atmosphere Department, Norwegian Institute for Air Research, PO Box 100, Kjeller, 2027, Norway k U.S. Geological Survey, Alaska Volcano Observatory, 4230 University Drive, Anchorage, AK 99508 USA l Université Libre de Bruxelle, Unité de Chimie Quantique et Photophysique, Campus du Solbosch, CP160/09, Avenue F.D. Roosevelt 50, 1050 Bruxelles, Belgium m MTU: Department of Geological/Mining Engineering & Sciences, 1400 Townsend Drive, Houghton MI 49931 USA n Le Studium, Institute for Advanced Studies, Orléans and Tours, France o L'Institut des Sciences de la Terre d'Orléans, l'Université d'Orléans, 1a rue de la Férollerie, 45071 Orléans, Cedex 2, France p Laboratoire de Géographie Physique, 1 Place A. Briand, 92195 Meudon Cedex, France
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 behaviour 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 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) were 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 30 km. Magma reached the surface with variable gas content resulting in alternating explosive and rapid effusive eruptions, and released a total of ~ 0.44 Tg of SO2. The eruptive behaviour seems also related to the seismicity along a tectonic fault more than 40 km 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.
► First scientific results from largest eruption in 100 years of Merapi volcano. ► Gas emissions were much higher than recorded at Merapi during past eruptions. ► Deep influx of gas-rich mafic magma triggered the eruption. ► Presence of an exsolved fluid phase coexistent with the pre-eruptive magma body. ► Eruption warnings by CVGHM and international team saved 10,000-20,000 lives.
1. Introduction Merapi stratovolcano is located 25–30 km north of the metropolitan area of Yogyakarta, Indonesia (Fig. 1) and the environs are home to around of 1.6 million people. It overlies the Java subduction zone and is composed mainly of basaltic-andesite tephra, pyroclastic flow, lava, and lahar deposits. Eruptions during the twentieth century typically recurred every 4 to 6 years and produced viscous lava domes that collapsed to form pyroclastic flows and subsequent lahars. These eruptions were relatively small, with typical eruptive volumes of 1– 4 × 106 m3 and magnitudes or volcanic explosivity indices (VEI) of 1–3 ( [Andreastuti et al., 2000], [Camus et al., 2000], [Newhall et al., 2000], [Voight et al., 2000a] and [Voight et al., 2000b]), where magnitude (Pyle, 2000) is given by [Me = log10(mass of products in kg) – 7].
Merapi volcano has been studied extensively by Indonesian and international teams, leading to improved understanding of the volcano's seismology ( [Hidayat et al., 2000], [Ratdomopurbo and Poupinet, 2000] and [Senschönefelder and Wegler, 2006]), deformation ( [Beauducel and Cornet, 1999], [Voight et al., 2000a], [Voight et al., 2000b] and [Young et al., 2000]), potential field geophysics ( [Jousset et al., 2000], [Zlotnicki et al., 2000] and [Tiede et al., 2005]), gas emissions ( [Le Guern and Bernard, 1982], [Nho et al., 1996], [Zimmer and Erzinger, 2003], [Humaida et al., 2007], [Toutain et al., 2009] and [Allard et al., 2011]), petrology ( [Gertisser and Keller, 2002], [Gertisser and Keller, 2003], [Chadwick et al., 2007], [Deegan et al., 2010] and [Deegan et al., 2011]), physical volcanology (Charbonnier and Gertisser, 2008) and lahar inundation (Lavigne et al., 2000). Merapi's high-temperature (400°– 850 °C) summit fumaroles, continuous gas emissions, and frequent small eruptions indicate an open and hot pathway for magma ascent to the near-surface. At the summit vent level, lava domes have typically plugged the uppermost part of the conduit except during eruptions when magmatic pressure built and new domes composed of mostly degassed magma extruded and collapsed or much more infrequently, gas-rich explosive eruptions occurred.
Fig. 1. Index map showing location of Merapi volcano summit and other features referred to in the text, e.g., observatory post stations (“Pos” in Indonesian), the Merapi Observatory and Technology Center (BPPTK), major drainages (abbreviated “K.” for “Kali” in Indonesian), short-period permanent seismic stations (full inverted triangles, PUS, DEL,PLA, KLA), temporary broadband stations (empty inverted triangles, LBH, GMR, GRW, PAS, L56 = WOR at summit). Cities and towns are indicated by name. In addition, hundreds of smaller villages are present on the flanks of the volcano. Major highways are indicated by heavy dashed-dotted lines and the read arcs at 10, 15, and 20 km radius distances from the summit indicate evacuation zones that were put into effect at different times during the eruptive activity (see text for details).
The lack of large explosive eruptions at Merapi during the several decades preceding 2010 is attributed to extensive degassing during ascent of the magma through the volcano's subsurface plumbing system (Le Cloarec and Gauthier, 2003). However, stratigraphic evidence shows that large explosive eruptions, such as the one that took place in 1872 (Hartmann, 1934) also occur. Because of the relatively open-pathway for magma ascent and the lack of explosive eruptions in the recent past, it was feared that precursors to such a large eruption might only be modest and inadequately appreciated. The increasing population on the volcano flanks meant that a large eruption could result in tens to hundreds of thousands of casualties.
Fortunately, although of short duration and rapidly escalating, large-magnitude precursors were recognized and identified in time to issue warnings for the impending large 2010 eruption, which had a VEI and Me of about 4.
We report on the monitoring techniques, data, and warning issues that came into play and were gathered during the 2010 eruptive sequence. Main explosive events occurred on 26 October (~ 10:00 utc), 29 October (~ 17:10–19:00 utc), 31 October (~ 7:30 and ~ 8:15 utc), 1 November (~ 3:00 utc), 3 November (~ 8:30 utc), 4 November (17:05 utc). We use a combination of petrologic, seismologic, geodetic, and gas emission data, along with remotely sensed observations of changes in morphology and eruption rate to propose a preliminary model for this „100-year‟ eruption.
In Section 2, we describe technical details of both “traditional” monitoring methods used at Merapi volcano and “state-of-the-art” satellite observations, extensively used during the 2010 eruption. In Section 3, we describe the chronology of the eruption and how our geophysical and satellite observations were interpreted, leading to timely warnings that saved 10,000– 20,000 lives. In Section 4, a preliminary eruption model is proposed, based on our analysis of the available monitoring signals and petrological data. Finally, we suggest that the management and decision-making during the crisis was successful thanks to a combination of long-term in-country expertise in dealing with volcanic crises and an unprecedented level of international collaboration. We conclude in summarising observations and interpretations on the eruption dynamics and propose a series of questions that need to be addressed for a better understanding of Merapi's most explosive eruption of the past 100 years.
2. Observational methods used during the 2010 Merapi eruption
Merapi has long been monitored using seismology, deformation, gas emission studies and petrology (Purbawinata et al., 1996) by CVGHM and its observatory and technology center in Yogyakarta (Balai Penyelidikan dan Pengembangan Teknologi Kegunungapian, or BPPTK).
Under non-eruptive conditions, the rate of inflation/deflation (measured as change in lengths of Electronic Distance Measurement (EDM) lines between the volcano's summit and flanks) is ~ 0.003 m d- 1; the cumulative seismic energy release is less than 35 MJ d- 1 with daily averages of 5 multiphase earthquakes and 1 volcano-tectonic earthquake; the baseline SO2 flux is ~ 50–100 Mg d- 1 ( [Nho et al., 1996] and [Humaida et al., 2007]), and the long-term eruption rate is 1.2 × 106 m3 y- 1 (Siswowidjoyo et al., 1995).
Deformation was measured using both tiltmeters near the summit and an Electronic Distance Measurement (EDM) network. The Electronic Distance Measurement (EDM) network utilized reflectors at high elevations on all flanks and measurements were carried out from five observation posts (Jrakah, Babadan, Selo, Kaliurang, and Ngepos) at distances of ~ 5– 10 km from the summit of Merapi.
Seismic monitoring and analysis were carried out in real time and used qualitatively during the crisis to infer magmatic and eruptive processes. Earthquake activity was monitored with four short-period (Mark Products L-4 seismometers) permanent stations (PUS, KLA, DEL,
and PLA, Fig. 1) and a real-time temporary broadband seismological network of five stations:
one Streikesen STS-2 (station LBH) and four Güralp CMG40T sensors (stations GMR, GRW, PAS, WOR) from July 2009 to September 2010, and then station L56 from September 2010).
Seismometers installed in July 2009 were part of the MIAVITA (MItigate and Assess risk from Volcanic Impact on Terrain and human Activities) European research project (Thierry et al., 2008). Technical problems including poor synchronization (lack of GPS signal) prevented a full analysis in real-time at some stations (GMR, L56, LBH).