Using Ground-Penetrating Radar to Unravel the Dynamics and Hazards of Block-and-ash Flows at Merapi Volcano, Indonesia
Abstract
Assessing the dynamics and depositional processes of block-and-ash flows (BAFs) can be extremely difficult when based on traditional field-based investigations alone, as these are often complicated by a combination of poor exposure, rapid lateral facies variations of associated deposits and unknown paleotopography. However, when combined with other techniques such as ground-penetrating radar (GPR), a method that allows the internal architecture of BAF deposits to be mapped to a depth of several meters at high resolution, many of the limitations of traditional field studies can be overcome. Merapi volcano in Central Java is one of the most frequently erupting volcanoes in Indonesia and a classic site for the study of BAFs. In a case study in the application of non-invasive geophysical investigations of BAF deposits, GPR was used to evaluate the dynamics and hazards of BAFs generated during the 2006 Merapi eruption. During the later eruption phases, BAFs affected areas on the volcano's southern flank when they spilled over the sides of existing river valleys to create overbank flows that extended across adjacent, densely populated interfluve (non-valley) regions. A GPR facies-based approach has been adopted in order to interpret radar sections and correlate the observed features to process-related information gained from outcrop descriptions and granulometric analysis. Across the whole deposit, distinct variations are evident with relatively uniform high-energy facies passing into more irregular, locally varying facies in the medial and overbank regions. These variations at larger (deposit) and smaller (intra-deposit) scale, which cannot be detected by traditional field-based studies alone, show that GPR is capable of being an important non-invasive tool for developing new, improved interpretations of BAF transport and emplacement dynamics and, ultimately, the hazards associated with such flows.
- Publication:
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AGU Spring Meeting Abstracts
- Pub Date:
- May 2009
- Bibcode:
- 2009AGUSM.V71B..03G
- Keywords:
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- 8414 Eruption mechanisms and flow emplacement;
- 8488 Volcanic hazards and risks;
- 8494 Instruments and techniques