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| Titel |
One Mother Two DADs: the two fault-related avalanches of Iriga, Philippines |
| VerfasserIn |
Engielle Mae Paguican, Alfredo Mahar Francisco Mahar, Benjamin van Wyk de Vries |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250048556
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| Zusammenfassung |
| Volcanic rock-slidedebris avalanches are low-frequency, high-volume events generated by volcanic sector collapse that begins as a rock-slide and progressively disintegrates on steep edifice slopes. They are linked to edifice instability and a triggering mechanism, related either to a volcanic event, extreme rainfall or tectonic movement. The case of the Iriga debris avalanche with a volume of 1.5 km2 and runout length of about 10 km has long been associated with a non-volcanic trigger. We revisit the debris field of Iriga avalanche to investigate its causal mechanisms and determine its time of occurrence. The absence of a soil layer between the pyroclastic flow (PF) deposit and hummocks, the mixture of the PF deposit with avalanche-related lava blocks, and hummocks comprised of PF deposits may indicate an eruptive event close in timing with respect to the debris avalanche. Also, a previously unidentified debris avalanche field in the west-northwest sector of Iriga volcano was identified. This debris avalanche is older than the more obvious debris avalanche field in the southeast sector, which is associated with a well-formed horseshoe-shaped amphitheatre crater. Both events are organised around a characteristic sigmoid structure- a negative flower structure caused by a major strike-slip fault that cuts the cone in two. The remaining structures on the cone and the avalanche structure are consistent with a fault movement related origin, and possible associated gravity spreading. Iriga serves as a textbook example of fault related volcanic landsliding that can be applied to other potential at risk volcanoes in strike-slip environments, such as Mayon. |
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