Project

Discipline

geophysical observations of Lusi; hydrothermal systems; volcano hydrogeology; modeling liquefaction

Lead
Le 6 mai 2006, sur l’île de Java en Indonésie, un séisme de magnitude 6.3 se produisit à Yogyakarta. Environ 48 heures plus tard, à 250 km de l’épicentre du séisme, dans la ville de Sidoarjo, une éruption de boue se produisit à la surface et donna naissance à LUSI. LUSI a rapidement accéléré sa croissance. La ville d’origine est maintenant enterrée sous 20m de boue qui s’étend sur 4 km2 retenue par un barrage de terre de 10m de haut. Toutes tentatives pour diminuer le débit de cette éruption ont échoué et personne ne sait quand cela pourra s’arrêter. De récentes recherches sur le déclencheur de cette catastrophe naturelle ont montré que les couches géologiques sous-jacentes, responsables de l’éruption, avaient une forme parabolique qui réfléchissaient et qui focalisaient l’énergie du séisme dans la couche d’argilite se trouvant à 1000m de profondeur et déjà soumise à de fortes pressions.
Lay summary
Aujourd’hui, LUSI se comporte comme un système particulier de source d’eau chaude qui jaillit par intermittence (Geyser) toutes les 60-120 secondes, avec une éjection de fluides à plus de 20 mètre de hauteur.  D’autres études géochimiques ont montré qu’à l’échelle tectonique, LUSI est d’une grande rareté. En effet, ce nouveau système hydrothermal est relié à un complexe volcanique proche. Ce projet vise à contraindre la dynamique de ce système. LUSI permet d’exploiter plusieurs horizons de recherches que se soient d’un système à grande échelle volcanique hydrothermal à une exploitation possible de l’énergie géothermale. Le but de ce projet est d’utiliser des outils géophysique, comme la gravimétrie et les méthodes magnétotelluriques afin de comprendre la géométrie du sous-sol et les écoulements régissant ce système hydrothermal jusqu’4-5 kilomètres de profondeur. Nous utiliserons aussi des outils de modélisations numériques pour contraindre les propriétés de ce système hydrothermal et estimer les mécanismes probables du à d’éventuel  futur tremblement de terre pouvant engendrer une liquéfaction à grande échelle dans cette région métastable.  Les résultats de cette recherche nous permettrons de comprendre la dynamique de ce système naturel complexe et rare.

Direct link to Lay Summary

Last update: 01.04.2015

Lead
On May 26, 2006 a magnitude 6.3 earthquake occurred in Yogyakarta on the Indonesian Island of Java, resulting in widespread death and destruction of this ancient city. About 48 hours later, in the town of Sidoarjo about 250 km from the earthquake epicentre, mud began to spill out onto the surface and Lusi was born. Lusi combines LUmpar (mud) and SIdoarjo where it occurred. Lusi quickly accelerated in output, peaking in August of 2006 with eruption rates up to 180,000 cubic meters of mud per day. The former town is now buried beneath about 20 meters of mud that extends over 4 square kilometres. Recent research into what triggered this natural disaster showed that the underlying geologic layers formed a parabolic shape that reflected and focussed the incoming seismic energy. The amplification of energy liquefied a mud layer at about 1000 m depth, allowing it to travel to the surface along a tectonic scale fault that runs through the center of the mud eruption.
Lay summary
Lusi continues today as a vigorous geyser system that erupts water and steam about every 60-120 seconds, with plume heights of about 20 meters. Other research from geochemistry showing that Lusi is likely a geological rarity of a newborn tectonic-scale hydrothermal system linked to the nearby volcano complex, and this project aims to constrain the dynamics of this system. Lusi  offers numerous research possibilities, from large-scale volcanic hydrothermal systems to possibile  geothermal energy exploitation. The focus of this project is to use geophysical tools such as gravity and magnetotelluric methods to constrain the subsurface geometry and flow paths from the hydrothermal fluids emanating from 4-5 kilometres. We will also use numerical modelling tools to constrain the hydrothermal properties of this system, and make mechanistic assessments of the possibility of large-scale liquefaction of the extruded mud layer to eventual future earthquakes in the region that can shake the metastable system. Results from this research will be a better understanding of the dynamics of this rare and complex natural system.

Direct link to Lay Summary

Last update: 01.04.2015

Active participation

We propose to conduct a suite of geophysical and laboratory investigations to constrain the lithological, geotechnical, hydrogeological and hydrothermal properties of the Lusi hydrothermal complex. Geophysical observations laboratory experiments will be used to constrain numerical modeling of a range of unsolved problems. Specifically, we propose (1) high-resolution micro-gravity studies of the Lusi eruption site and its southward extension towards the active volcanic complex, (2) Magnetotelluric (MT) surveys of the eruption site to constrain dominant fluid pathways in the subsurface, (3) MT studies to the south of the eruption site to search deeper levels for a sill intrusion hypothesized to be hydrothermally driving this system, (4) Geo-electric studies study the shallow subsurface and calibrate our other geophyiscal measurements, (5) Process and incorporate seismic reflection profiles into hydrogeological hydrothermal numerical models, (6) photogrammetry studies using the existing drone at Lusi to explore the possibility that Lusi represents a natural meso-scale analog to plate tectonics, and (7) active seismic surveys to constrain the geometry of the mud basin. We will collaborate closely and synthesize data with other ongoing geochemical and passive seismic monitoring investigations. We also propose to perform numerical modeling studies constrained by geophysical observation to (1) Create 3D geological models to investigate the large-scale hydrogeological and hydrothermal properties of this mud eruption/volcanic arc system. (2) Develop and investigate reactive transport models constrained by geochemical observations acquired from the Lusi vent and surroundings, (3) Couple wave propagation codes to liquefaction models to investigate i) eruptive properties in response to incoming energy of nearby and distant earthquakes and constrained by seismic observations, and ii) assess the potential for a catastrophic and very hazardous event of large-scale liquefaction of the evolved mud basin, and (4) Further develop models of geyser behavior to constrain the properties of the roots of this system.