267 research outputs found
FLOWS - Booklet of Short Term Scientific Missions
Booklet of Short Term Scientific Missions carried out during the COST Action "Impact of Fluid circulation in old oceanic Lithosphere on the seismicity of transfOrm-type plate boundaries: neW solutions for early seismic monitoring of major European Seismogenic zones
Detection of Lahar Flow Direction from Semeru Eruption on 4 December 2021 using Gravity Method
Mount Semeru, an active, steep-sided volcano in East Java, erupted on 4 December 2021 following extreme rainfall that led to an avalanche of hot pyroclastic flows and lahars. Besides a debatable eruption source with no preceding seismic signals observed, it has drawn the international community's attention for its extent of largely impacted areas down the summit. In this study, we used gravity method modeling of the local anomaly in density distribution after the event to determine the unique pattern of the lahar flow direction with the corresponding extent and the spread of the flow. The data were collected from a TOPEX satellite altimeter and processed using a number of specific techniques to obtain a contoured map of local anomaly. The results showed that the main path of the flow was found to descend down the slope to the southeast of the crater, extending to a distance of about 20 km with a maximum lahar flow width of about 2 km toward agricultural lands and populated areas, consistent with the high-resolution satellite imagery produced by UNOSAT-UNITAR. It suggests that gravity anomaly could be used to simulate the flow pattern and the widespread damage of volcanic materials after an eruption.DOI: 10.17977/um024v7i22022p07
Site and Basin Effects on Seismic Hazard in Indonesia:Sulawesi and Jakarta Case Studies
Earthquakes are among the most costly, devastating and deadly
natural hazards. The
extent of the seismic hazard is often influenced by factors like
the source location and site
characteristics, while the susceptibility of assets is influenced
by the population density,
building design, infrastructure and urban planning. A
comprehensive knowledge of the
nature of source and local geology enables the establishment of
an effective urban planning
that takes into account the potential seismic hazard, which in
turn may reduce the degree
of vulnerability.
The first probabilistic seismic hazard assessment (PSHA)
incorporating the effects of local site characteristic for the
island of Sulawesi in Indonesia has been conducted.
Most of the island, with the exception of South Sulawesi, is
undergoing rapid deformation.
This leads to high hazard in most regions (such that PGA > 0.4g
at 500 year return period
including site effects) and extremely high hazard (like PGA > 0.8
g at 500 year return
period) along fast-slipping crustal fault. On the other hand, a
distant site relative to fault
might suffer higher ground motion if that site is composed of
soft soil. This research has
proven that incorporating near-surface physical properties, in
this case is represented by
VS30, surface geology contribute significantly to ground motions,
consequently, responsible
for potential building damage.
The PSHA study that took place in Sulawesi took us move further,
investigate
the effect of deep structure on seismic waves. Jakarta was chosen
for its location sitting
on less known deep sediment basin and economic and political
importances. A dense
portable-seismic-broadband network, comprising 96 stations, has
been operated within
four months covering the Jakarta. The seismic network sampled
broadband seismic-noise
mostly originating from ocean waves and anthropogenic activity.
We used Horizontal-toVertical Spectral Ratio (HVSR) measurements
of the ambient seismic noise to estimate the
fundamental-mode Rayleigh wave ellipticity curves, which were
used to infer the seismic
velocity structure of the Jakarta Basin. By mapping and modeling
the spatial variation of
low-frequency (0.124{0.249 Hz) HVSR peaks, this study reveals
variations in the depth to
the Miocene basement. To map these velocity profiles of unknown
complexity, we employ
a Transdimensional-Bayesian framework for the inversion of HVSR
curves for 1D profiles
of velocity and density beneath each station. The inverted
velocity profiles show a sudden
change of basement depth from 400 to 1350 m along N-S profile
through the center of the
city, with an otherwise gentle increase in basin depth from south
to north.
Seismic wave modelings are conducted afterward and shows that for
very deep
basin of Jakarta, available ground motion prediction equation
(GMPE) is less sufficient
in capturing the effect of basin geometry on seismic waves.
Earrthquake scenario modeling using SPECFEM2D is performed to
comprehend the effect of deep basin on ground
motions. This modeling reveals that the city may experience high
peak ground velocity
(PGV) during large megathrust earthquake. The complexity of the
basin is responsible
for magnifying ground motions observed in the basin
Booklet of Participants â FLOWS
Booklet of Participants of the COST ACTION "Impact of Fluid circulation in old oceanic Lithosphere on the seismicity of transfOrm-type plate boundaries: neW solutions for early seismic monitoring of major European Seismogenic zones (FLOWS
Solid earth science in the 1990s. Volume 2: Panel reports
This is the second volume of a three-volume report. Volume 2, Panel Reports, outlines a plan for solid Earth science research for the next decade. The science panels addressed the following fields: plate motion and deformation, lithospheric structure and evolution, volcanology, Earth structure and dynamics, Earth rotation and reference frames, and geopotential fields
Progress in Volcanology
Progress in Volcanology includes nine chapters in three sections. The first section is the âIntroductionâ while the other two sections speak on âApplied Volcanologyâ and âVolcanic Sedimentology, Geochemistry and Petrology.â The chapters address volcanology in several areas around the world, including Italy, Indonesia, Ethiopia, Argentina, India, and others
Modeling volcanic unrest by data assimilation
Volcanic activity may lead to potential volcanic eruptions, but it also provides critical information for understanding the physical processes within a volcanic system. Combining multiple observations and advanced physical models allows us to explore the response of the surrounding host rock to changes in the physical condition in a magmatic system. This work focuses on developing and applying a robust data-model fusion framework to investigate the mechanisms involved in volcanic unrest, such as deformation, failure, and pore fluid migration. First, using a series of tests based on the synthetic data, I optimize a data assimilation technique, Ensemble Kalman Filter (EnKF), to improve its performance in forecasting volcanic unrests with multiple geodetic observations. Then, the robustness of the EnKF is confirmed in application to the unrest and 2009 eruption of Kerinci volcano, Indonesia. To understand the effects of uncertain rheology on our model results, I conduct a systematic sensitivity study to determine the impact of rheology on the host-rock failure prediction. With a better understanding of the uncertainties in my models, I establish numerical models by integrating multiple observations to investigate the magma reservoir dynamics, crustal stress, failure-related seismicity, and hydrological interactions of two different magmatic systems, Laguna del Maule in the Andes, Chile, and Atka in the Aleutian, USA. In both systems, the pre-existing structures and pore fluids play critical roles in catalyzing seismicity, redistributing masses, and delaying/trigger eruptions
Geospatial Assessment of Coseismic Landslides in Baturagung Area
Java, the most densely populated island in Indonesia, is located on top of the most seismically active areas in Southeast Asia: the Sunda Megathrust. This area is frequently hit by strong earthquake. More than 3,300 M>5earthquakesoccurred between 1973-2014. The wide range of mountainous areas and high intensity of rainfall, make several part of the island one of the most exposed regions for coseismic landslides such as Baturagung area, the Southeast mountainous area of Yogyakarta Province. An integrated method between RS and GIS was used to conduct the vulnerability assessment due to the lack of the site specific slope instability analysis and coseismic landslides data. The seismic zonation of Baturagung area was obtained based on the analysis of Kanai attenuation. The geologic information was extracted using remote sensing interpretation based on the 1:100,000 geologic map of Yogyakarta and geomorphologic map of Baturagung area as well. The coseismic landslide hazard assessment has been estimated using scoring analysis in the GIS platform proposed by Mora and Vahrson (1993) with several modification. The accomplished coseismic landslide hazard map shows medium hazard coverage in the eastern areas, in the upper slope of Baturagung area, which consists of Semilir Formation. The result provides a distinct description of coseismic landslides hazard distribution in Batuaragung area. However, it should only be the preliminary assessment of the site specific investigation especially on valuable area or asset
Monitoring von Hangbewegungen mit InSAR Techniken im Gebiet Ciloto, Indonesien
In this doctoral thesis, the InSAR techniques are applied to detect the ground movement phenomenon and to assess the InSAR result geometrically in the Ciloto area, Indonesia. Mainly, one of those techniques, the SB-SDFP algorithm, overcomes the limitations of conventional InSAR in monitoring rural and agricultural areas and can observe extremely slow landslides. The InSAR strategy is positively known as a promising option to detect and quantify the kinematics of active landslides on a large areal scale.
To minimize the bias of the InSAR displacement result, the correction of the tropospheric phase delay was carried out in a first step. This procedure is demonstrated in experiments both in the small study area in Ciloto and in a larger area. The latter is an area located in Northern Baja California, Mexico and is dominated by tectonic activity as well as groundwater-induced subsidence. A detailed investigation of the slope movement's behavior in the Ciloto district was conducted utilizing multi-temporal and multi-band SAR data from ERS1/2 (1996-1999), ALOS PALSAR (2007-2009) and Sentinel-1 (2014-2018) satellites. The region was successfully identified as a permanent active landslide prone area, especially in the vicinity of the Puncak Pass and Puncak Highway. The full 3D velocity field and the displacement time series were estimated using the inversion model. The velocity rate was classified from extremely slow to slow movement.
To comprehend the landslide's behavior, a further examination of the relationship between InSAR results and physical characteristics of the area was carried out. For the long period of a slow-moving landslide, the relationship between precipitation and displacement trend shows a weak correlation. It is concluded that the extremely slow to slow deformation is not directly influenced by the rainfall intensity, yet it effectuates the subsurface and the groundwater flow. The run-off process with rainfall exceeding a soil's infiltration capacity was suspected as the main driver of the slow ground movement phenomenon. However, when analyzing rapid and extremely rapid landslide events at Puncak Pass, a significant increase in the correlation coefficient between precipitation and displacement rate could be observed.In dieser Doktorarbeit wird die Anwendung von erweiterten Verarbeitungsstrategien von InSAR Daten zur Erkennung und geometrischen Bewertung der Bodenbewegungen im Ciloto - Indonesien dargestellt. Dieser Ansatz ĂŒberwindet die BeschrĂ€nkungen konventioneller SAR-Interferometrie und ermöglicht sowohl ein kontinuierliches Monitoring dieses landwirtschaftich geprĂ€gten Gebietes als auch die Erfassung extrem langsamer Hangrutschungen.
Um eine Verzerrung der InSAR Deformationsergebnisse zu minimieren, wurde zunĂ€chst eine Korrektur der troposphĂ€rischen Phase durchgefĂŒhrt. Diese neuartige Strategie wird sowohl im Forschungsgebiet Ciloto als auch an einem gröĂeren Gebiet demonstriert. Bei letzterem handelt es sich um einen KĂŒstenstreifen im nördlichen Niederkalifornien, Mexiko, welcher durch hohe tektonische AktivitĂ€t und grundwasserinduzierte Landsetzungen charakterisiert ist. Die detaillierte Untersuchung des Verhaltens von Hangrutschungen im Ciloto erfolgte durch die Verarbeitung multi-temporaler SAR-Daten unter Nutzung verschiedener FrequenzbĂ€nder, darunter ESR1/2 (1996-1999), ALOS PALSAR (2007-2009) und Sentinel-1 (2014-2018) Daten. Die Region konnte erfolgreich als permanent aktives Hangrutschungsgebiet identifiziert werden, wobei der Puncak Pass und der Puncak Highway ein erhöhtes Gefahrenpotential aufweisen. Ein 3D- Geschwindig-keitsfeld der Deformation und die zugehörigen Zeitreihen wurden mit dem Inversionsmodell berechnet. Die Geschwindigkeitsrate wurde als langsam bis extrem langsam klassifiziert.
Um das dynamische Verhalten der Hangrutschung zu verstehen wurde, in einer weiteren Untersuchung die Beziehung zwischen dem InSAR-Ergebnis und den physikalischen Begebenheiten im Forschungsgebiet analysiert. Es wird der Schluss gezogen, dass die langsame bis extrem langsame Verformung nicht direkt von der NiederschlagsintensitĂ€t beeinflusst wird, diese sich aber auf den Untergrund und die Grundwasserströmung auswirkt. Es wird vermutet, dass der OberflĂ€chenablauf, welcher die InfiltrationskapazitĂ€t des Bodens ĂŒbersteigt, ausschlaggebend fĂŒr das PhĂ€nomen der langsamen Bodenbewegung ist. FĂŒr die schnellen und extrem schnellen Hangrutschungen jedoch konnte eine signifikante Erhöhung des Korrelationskoeffizienten zwischen Niederschlag und Verschiebungsrate bei Untersuchungen der Hangrutschung am Puncak-Pass nachgewiesen werden
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