Publication Date:
2017-04-04
Description:
The spectacular Indonesian Lusi mud eruption started in May 2006 following to a 6.3 M earthquake striking
the island of Java (Mazzini et al., 2007). Previous studies investigated the mechanisms of reactivation of the
Watukosek fault system that crosses Lusi locality (Mazzini et al., 2009) and continues to the NE of Java. Results
show that the quake triggered lateral movement of this strike-slip system resulting in several aligned eruptions sites
including Lusi. Geochemical studies of the erupted fluids reveal a mantle signature and point to a connection with
the neighboring Arjuno-Welirang volcanic complex (Mazzini et al., 2012) indicating that Lusi is a sedimentary
hosted geothermal system.
In order to estimate the amount of gas that is being released around the Lusi crater ( 7 km2), we recently
conducted a survey of over 300 stations (CO2 and CH4 flux measurements) using a closed-chamber flux-meter
system and collected gas samples to analyze the composition of the seeps. In addition 20 soil gas concentrations
were collected using a steel probe driven into the ground to a depth of 0.7-0.8 m to avoid the major influence of
meteorological variables.
Results show that the highest CO2 flux is present along the NE-SW oriented Watukosek fault (with peaks up to
400 g/m2day) and along the E-W oriented Siring antithetic fault (with peaks up to 110 g/m2day). The pools
have overall a CH4-dominated composition, while the dry fault-related fractures are CO2-dominated which is in
agreement with higher recorded temperatures at these sites. Flux measurements in the seeping pools reveal that
CO2 flux is an order of magnitude higher than that measured in the fault zones, and two order of magnitude for
CH4 flux.
C02 and CH4 microseepage is occurring in significant amount throughput the mud-covered area with average
values of 297 and 95 g/m2day, respectively. CH4 flux shows the highest values in the W and NW sector of the
Lusi area, while CO2 flux highlights the presence of three areas characterized by high values, in the northern,
southern and western sectors.
Methane concentrations show high values (maximum value 1490 ppm) in the eastern part of Lusi crater, while
CO2 show low values (maximum value 11580 ppm) along the west Lusi profile.
Description:
Unpublished
Description:
Vienna
Description:
7A. Geofisica di esplorazione
Description:
restricted
Keywords:
Gas flux
;
seep
;
03. Hydrosphere::03.04. Chemical and biological::03.04.05. Gases
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
Oral presentation
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