--> --> Abstract: Causes and Triggers of the Lusi Mud Volcano, Indonesia, by Adriano Mazzini, Henrik Svensen, Sverre Planke, and Grigorii Akhmanov; #90082 (2008)

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Causes and Triggers of the Lusi Mud Volcano, Indonesia

Adriano Mazzini1, Henrik Svensen1, Sverre Planke2, and Grigorii Akhmanov3
1Physics of Geological Processes, University of Oslo, Oslo, Norway
2Volcanic Basin Petroleum Research, Oslo, Norway
3Faculty of Geology, Moscow State University, Moscow, Russian Federation

The 29th of May 2006 a sudden eruption of 100 °C mud and gas started in NE Java . The flow rate of this new mud volcano (named LUSI) escalated up to 180000 m3/d and still seems unstoppable.

The initial eruption occurred in the proximity of an exploration well two days after a 6.3 earthquake that struck the southern part of Java. To date, there is little doubt about the natural causes of the eruption, however the investigations regarding the triggering (i.e. man-made or earthquake induced) still continue.

Pre-eruption seismic data show a subsurface piercing feature imaged at the future eruption site. This feature is situated on a fault that crosses Java with a SW-NE direction hosting other mud volcanoes. Sampling and field observations show that the 27th of May seismic event altered the critical equilibrium in the region and contributed to trigger the LUSI eruption. Indisputably the SW-NE oriented fault was reactivated after this earthquake and controlled the eruption dynamics as well as the ongoing regional collapse. A regional high T gradient triggers mineralogical transformations and geochemical reactions at shallow depth. It is proposed a mechanism where the eruptions started following the 27th of May earthquake due to fracturing and accompanied depressurization of >100 °C pore fluids from > 1700 m depth. The monitoring of the LUSI flow rate still shows peaks after each seismic activity in the region. Ongoing SW-NE oriented collapse around the crater indicates that the fault is still strongly affected by seismicity.

The hypothesis that the neighbouring drilling triggered the eruption cannot be ruled out, however, so far, no convincing data has been presented to support this hypothesis. Seismic events with the epicentre located few hundreds (and sometimes thousands) km away are known to have triggered the eruption of “naturally prepared” systems.

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