Doppler radar monitoring of lava dome processes at Merapi Volcano, Indonesia

Merapi volcano in Central Java, Indonesia, is considered one of the most dangerous volcanoes worldwide. Due to the high viscosity of its magma, the lava emerging at the top the volcano cannot flow silently down the flanks of the volcano but builds a lava dome. An indicator for the stability of the lava dome are rockfalls and block and ash flows, which are caused by local instabilities at the dome. When the lava dome reaches a critical size, it collapses. This results in dangerous block and ash flows, which can reach several kilometers into the proximity of the volcano. In the past rockfall and block and ash flow activity has been observed visually or by seismic networks. However, visual observations are often impossible due to bad visibility conditions and until now seismic measurements allow only few insights into the dynamic processes that are involved in instability events, i.e. events of material breaks off the lava dome. In order to enhance monitoring of lava dome activity, a first prototype Doppler radar system has been installed at the western of the Merapi in October 2001. This system consists of a frequency modulated continuous wave (FMCW) 24GHz Doppler radar. The Doppler spectra recorded by the system give a relative measure of the amount of material moving through the beam as well as information about its velocities. Because the radar system is insensitive for clouds, the system provides first continuous "quasi-visual" observations of dome instabilities...thesi

The eye in the sky: Avalanche mapping from space

The Seward Highway in Alaska has over one hundred avalanche paths spread out along a 150 km major transportation corridor, which traverses three different avalanche climatic regimes. This coupled with a small staff can make avalanche debris detection and mapping difficult. With the use of satellite imaging we may have a reliable means of detecting and recording avalanche deposits. During the winter of 2016 the Seward Highway recorded an unprecedented amount of glide avalanche releases. Using SAR imagery we can accurately detect avalanche debris, further aiding in mitigation strategies and avalanche hazard management

The EU Center of Excellence for Exascale in Solid Earth (ChEESE): Implementation, results, and roadmap for the second phase

publishedVersio

2.5D Inversion and Joint Interpretation of CSEM Data at Sleipner CO2 Storage

In this paper, we revisit the marine controlled-source electromagnetic (CSEM) data, acquired above the Sleipner CO2 storage, in order to further study the dataset and conclude the feasibility of marine CSEM for offshore CCS monitoring. There are some challenges with respect to CSEM in this particular area: 1) strong airwave influence (due to regional shallow water depth); 2) potential of weak resistivity anomaly; 3) seabed pipeline network; and 4) rather shallow target depth. We are yet able to extract useful information; interpret further the CSEM inversion results by combining seismic data; and to extract the in situ resistivity and saturation of CO2 in the Utsira formation by applying a rock physics model. In addition, to minimize the influence of the seabed pipeline on the CSEM data, we have muted some of data and receivers near the seabed pipeline network. The results show a good agreement with seismic data, and the estimated total mass of CO2 agrees well with the injection data. This current study confirms that the marine CSEM can be an important and essential tool for offshore CO2 storage monitoring, yet not alone but when combined with both seismic and gravity. Finally, near-future large-scale CCS projects in the North Sea would require extensive infra-structures such as seabed pipeline, etc. This study demonstrates that CSEM may work even with such infra-structures in place.publishedVersio

2.5D Inversion and Joint Interpretation of CSEM Data at Sleipner CO2 Storage

In this paper, we revisit the marine controlled-source electromagnetic (CSEM) data, acquired above the Sleipner CO2 storage, in order to further study the dataset and conclude the feasibility of marine CSEM for offshore CCS monitoring. There are some challenges with respect to CSEM in this particular area: 1) strong airwave influence (due to regional shallow water depth); 2) potential of weak resistivity anomaly; 3) seabed pipeline network; and 4) rather shallow target depth. We are yet able to extract useful information; interpret further the CSEM inversion results by combining seismic data; and to extract the in situ resistivity and saturation of CO2 in the Utsira formation by applying a rock physics model. In addition, to minimize the influence of the seabed pipeline on the CSEM data, we have muted some of data and receivers near the seabed pipeline network. The results show a good agreement with seismic data, and the estimated total mass of CO2 agrees well with the injection data. This current study confirms that the marine CSEM can be an important and essential tool for offshore CO2 storage monitoring, yet not alone but when combined with both seismic and gravity. Finally, near-future large-scale CCS projects in the North Sea would require extensive infra-structures such as seabed pipeline, etc. This study demonstrates that CSEM may work even with such infra-structures in place.publishedVersio

The use of SAR interferometry for landslide mapping in the Indian Himalayas

-The aim of the here presented research was to investigate the potential of two-pass differential InSAR, and advanced DInSAR techniques, such as Small Baseline Subset (SBAS) and Persistent Scatterers (PS) interferometry, in order to detect and monitor the temporal behaviour of surface deformations in selected areas of the Garhwal and Kumaon Himalaya. We present results from the surroundings of the town of Nainital, from the Mansa Devi Hills area, and the areas around the cities of Chamoli Gopeshwar and Joshimath

(Table 2) Picked maximum velocities from 3 radars (RAY, SHK, and SUM), showing 10 explosions at Erebus volcano, Antarctica, and their respective directivity vectors

We used a novel system of three continuous wave Doppler radars to successfully record the directivity of i) Strombolian explosions from the active lava lake of Erebus volcano, Antarctica, ii) eruptions at Stromboli volcano, Italy, and iii) a man-made explosion in a quarry. Erebus volcano contains a convecting phonolite lava lake, presumably connected to a magma chamber at depth. It is one of the few open vent volcanoes that allow a direct observation of source processes during explosions. Its lava lake is the source of frequent violent Strombolian explosions, caused by large gas bubbles bursting at the lake surface. The exact mechanism of these bubble bursts is unclear, as is the mechanism of the creation of the infrasound signal accompanying the explosions. We use the Doppler radar data to calculate the directivity of Strombolian eruptions at Erebus. This allows us to derive information about the expected type of infrasound source pattern (i.e. the role of a dipole in addition to the monopole signature) and the physical structure of the volcano. We recorded 10 large explosions simultaneously with three radars, enabling us to calculate time series of 3D directivity vectors (i.e. effectively 4D), which describe the direction of preferred expansion of the gas bubble during an explosion. Such directivity information allows a comparison to dipole infrasound radiation patterns recorded during similar explosions only a few weeks later. Video observations of explosions support our interpretation of the measurements. We conclude that at Erebus, the directivity of explosions is mainly controlled by random processes. Since the geometry of the uppermost conduit is assumed to have a large effect on the directivity of explosions, the results suggest a largely symmetrical uppermost conduit with a vertical axis of symmetry. For infrasound recordings, a significant dipole signature can be expected in addition to the predominant monopole signature