Criterios de selección para el diagrama de bloques

4.1. Introduction

The October-November 2010 eruption of Merapi volcano was the largest eruption (VEI 4) over the past 140 years. Previously, Merapi volcano was better known for smaller dome-collapse eruptions every 2-6 years on average, and ‘large’ explosive episodes every 8-15 year (Thouret et al., 2000). The 20th _{Century Merapi eruptions typically} produced summit lava domes, which collapsed to generate block-and-ash pyroclastic flows (BAFs), previously known as “Merapi type” “nuées ardentes”, a category of pyroclastic density currents (PDCs). In addition to lava domes extrusions, the 2010 eruption also produced several powerful explosions, vertical eruption columns up to 17 km altitude and numerous PDCs that extended into populated areas at distances as far as 16 km from the summit (Surono et al., 2012). On the other hand, this remarkable event demonstrated the effective crisis management by Indonesian authorities together with the involvement of international scientific cooperation. Between 26 October and 8 November 2010, the eruptive events around Merapi caused 376 people were lost their lives and about 400,000 people were displaced (Mei et al. 2013), but timely forecasts delivered by the Center for Volcanology and Geological Hazard Mitigation (CVGHM) and prompt evacuations of many tens of thousands of people saved as many as 10,000- 20,000 lives (Surono et al., 2012). The role of international collaborators was also critical in delivering near-real-time data and advice that complemented the extensive experience of CVGHM in interpreting the eruptive activity of Merapi.

Continuous research efforts inverted on Merapi for decades have been directed at understanding the mechanisms of dome extrusion and subsequent collapse “Merapi- type” eruptions and at improving eruption forecasting. In addition, the 2010 Merapi eruption has offered a rich set of scientific data to be analyzed and interpreted in order to advance in the understanding of, and ability to forecast, explosive volcanism. Such research studies have been carried out and published, for example in the special issue of the Journal of Volcanology and Geothermal Research, volume 261, in 2013 (Jousset et al.,

2013). Published studies have covered a wide range of research fields and volcanological topics including the application of satellite remote sensing. During the 2010 Merapi crisis, satellite remote sensing data have been integrated with seismic data for near-real time monitoring of the eruption to a point that interpretation did play role in decision support, especially with respect to the deleniation of exclusion zones (Surono et al., 2012). Measurements of SO2 emissions and maps of volcanic cloud dispersal from satellite remote sensing were available and useful during the most explosive phases of eruption. Synthetic Aperture Radar (SAR) imagery, capable of providing information during day or night and independent of the meteorological conditions, has been shown to be useful for recurrent monitoring of Merapi volcano during the crisis (Pallister et al., 2013), defining ground surface displacement (Saepuloh et al., 2013), evaluating the extent of impacts (Yulianto et al., 2013; Solikhin et al., 2015a) and estimating deposit volume (Bignami et al., 2013). Satellite multispectral (optical) imagery has been used to support the field investigations and to estimate their volume (Cronin, et al., 2013; Komorowski et al., 2013; Charbonnier et al., 2013; Jenkins et al., 2013; Solikhin et al., 2015b).

The methodological work of analysis of PDCs and other erupted materials using satellite imagery has a clear potential for helping the volcanological community to contribute to decision making process during a volcano crisis. Our study, presented in the fourth chapter, aims to assess the extent and effects of the 2010 Merapi PDCs, tephra-fall and subsequent lahars based on remote sensing techniques using HSR optical imagery. We used the most recent HSR imagery data sets from Pléiades, GeoEye, QuickBird and SPOT5 satellites and aerial photographs, acquired before and after the eruption. Among them Pléiades sensor has been used for the first time to identify and map pyroclastic deposit immediately after a large eruption. Pléiades, GeoEye, QuickBird and other HSR images offers unprecedented detail for mapping pyroclastic deposit on otherwise unaccessible active volcanoes. These data sets have enabled us to provide additional insight into the chronology, dynamics, and impacts of the volcanic eruption, which are complementary to previous detailed studies. This chapter encompasses several studies of the 2010 Merapi eruption including: (1) a new estimate of volumes of tephra-fall deposits using three empirical calculation methods (exponential, power-law and Weibull thinning); (2) the effects of the eruption and structural changes on the volcano summit; (3) the extent of pyroclastic deposits in the Gendol-Opak catchments; (4) the origin of

post-eruption lahar deposits; and (5) the behavior of the overbank PDCs and lahars based on the analysis of geomorphometric indices related to river channels.

4.2. High-spatial resolution imagery of the 2010 Merapi Volcano eruption

This section corresponds to an article that has been accepted for publication in the Bulletin of Volcanology on 6 Feburary 2015.

High-spatial resolution imagery helps map deposits of the large (VEI 4) 2010 Merapi Volcano eruption and their impact

Akhmad Solikhin1, 2_{, Jean-Claude Thouret}2_{, Soo Chin Liew}3_{, Avijit Gupta}3, 4_, Dewi Sri Sayudi1_{, Jean-François Oehler}5_{, Zeineb Kassouk}2

1 _{Center for Volcanology and Geological Hazard Mitigation, Jalan Diponegoro 57,}

Bandung Indonesia

2 _{Clermont Université, Université Blaise Pascal, Laboratoire Magmas et Volcans}

UMR 6524 CNRS, IRD-R163 and CLERVOLC, 5 rue Kessler, 63038, Clermont Ferrand cedex, France

3 _{Center for Remote Imaging, Sensing and Processing, National University of}

Singapore, Singapore

4 _{School of Earth and Environmental Sciences, University of Wallongong, Australia} 5 _{Altran Ouest, Technopôle Brest Iroise, Site du Vernis CS 23866, 29238 Brest cedex}

3, France

Published in Bulletin of Volcanology, Volume 77, Issue 3, March 2015, Article 20

RESEARCH ARTICLE

High-spatial-resolution imagery helps map deposits of the large