Three-dimensional Digital Mapping of the Noboribetsu Geothermal Field, Kuttara Volcano, Hokkaido, Japan, using a Helicopter-borne High-resolution Laser Scanner
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Laser Scanning
Volcanic ash
Earth observation satellite
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Digital surface
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<p>Located about 30 km north of the city of Yogyakarta, Merapi is considered as one of the most dangerous volcano of Indonesia with 3000 to 5000 fatalities since 1672 and about two million people living at less than 30 km from the crater. The recent eruptive history of Merapi is characterized by two eruptive styles: 1) recurrent effusive growth of viscous lava domes, with gravitational collapses producing pyroclastic flows known as &#171; Merapi-type nu&#233;es ardentes &#187; (VEI 2); 2) more exceptional explosive eruptions of relatively large size (VEI 3-4), associated with column collapse pyroclastic flows reaching distances larger than 15 km from the summit. The eruptive periodicity is 4 to 5 years for the effusive events and 50 to 100 years for the explosive ones. The last explosive events (VEI 3-4) occurred in November 2010 and opened a 500m wide and 250m deep crater. After the 2010 eruption, the activity has been reduced. We used TerraSAR-X data to characterize eruptive deposits emplaced during the 2010 event as well as sudden destabilization of crater walls. The activity increased significantly during the spring of 2018 when several phreatic eruptions were recorded with ash emission reaching an elevation of more than 5 kilometers. The 11<sup>th</sup> of August 2018 a new dome was observed inside the summit crater, thus marking the start of a new phase of effusive activity. It is essential to be able to quantitatively follow the temporal evolution of the dome shape and volume through time as its potential destabilisation would produce pyroclastic flow on the volcano flank. A time series of five tri-stereo Pleiades optical images, acquired between February and September 2019, is used to produce High Resolution DEMs of Merapi summit area with a spatial resolution of 3 m and a vertical precision of 1 m. By using a DEM derived from Pleiades stereo images acquired in April 2013 as a reference, the dome volume evolution through time is estimated. We show that the dome had already reached a volume around 0.5 Mm<sup>3</sup> (+- 0.02Mm<sup>3</sup>) end of February 2019 corresponding to a mean effusive rate of 3000 m<sup>3</sup>/day during 6 months and that its size remained constant after February 2019. These results are consistent with volume estimations derived from drone measurements. However DEMs derived from Pleiades images enable to monitor a larger area and reveal accumulation of eruptive deposits due to dome destabilization a few hundreds of meters below the dome. The magma effusive rate thus remained significant but was reduced to 250 m<sup>3</sup>/day from February to September 2019.</p>
Dome (geology)
Phreatic eruption
Lava dome
Elevation (ballistics)
Phreatic
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New maps of the summit of Mount Etna volcano (1:5000–1:4000), derived from helicopter photogrammetry, thermal images and terrestrial laser scanner survey, are here presented. These maps indicate the main morpho-structural changes occurring during the powerful explosive and effusive eruptions involving the summit craters of Etna over the first two weeks of December 2015. The survey enabled identifying the proximal erupted volume (7.2 ± 0.14 × 106 m3) and the size and location of the vent causing the powerful explosive activity inside the Central Crater. Our survey also outlines the growth of a recent (2011–2015) summit cone on top of a former pit crater, named New SE-Crater. This new cone is by now comparable in size to the former SE-Crater. The shape and size of two small cinder cones that formed on the upper eastern flank of the summit zone in May–July 2014 are also shown. This approach can be used in fast and frequent monitoring of very active volcanoes.
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Volcanology
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Thermal infrared
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Seismic Noise
Seismic interferometry
Seismic Tomography
Ambient noise level
Geophysical Imaging
Passive seismic
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Tracking the level of the lava lake in Halema‘uma‘u Crater, at the summit of Kīlauea Volcano, Hawai’i, is an essential part of monitoring the ongoing eruption and forecasting potentially hazardous changes in activity. We describe a simple automated image processing routine that analyzes continuously-acquired thermal images of the lava lake and measures lava level. The method uses three image segmentation approaches, based on edge detection, short-term change analysis, and composite temperature thresholding, to identify and track the lake margin in the images. These relative measurements from the images are periodically calibrated with laser rangefinder measurements to produce real-time estimates of lake elevation. Continuous, automated tracking of the lava level has been an important tool used by the U.S. Geological Survey’s Hawaiian Volcano Observatory since 2012 in real-time operational monitoring of the volcano and its hazard potential.
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Tracking (education)
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Deformation monitoring
Volcanology
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Focused on the Stromboli Island, this research investigates whether airborne remote sensing systems, such as those based on digital photogrammetry and laser scanner sensors, can be adopted to monitor slope deformation and lava emplacement processes in active volcanic areas. Thanks to the capability of extracting accurate topographic data and working on flexible time schedule these methods can be used to constrain the regular and more frequent measurements derived from satellite observations. In this work we present an application dedicated to the monitoring of Stromboli volcanic edifice useful to obtain quantitative data on the geometry of deformation features and the displaced (failures and landslides) and emplaced (lava flows) volumes. In particular, we focused on the capability of extracting average effusion rates from volume measurements that can be used to validate or integrate satellite derived estimates are often affected by biases which are not easily detectable. Since 2001 a number of airborne remote sensing surveys, namely Digital Photogrammetry (DP) and Airborne Laser Scanning (ALS), were carried out on Stromboli volcano to obtain high resolution digital terrain models (DEM) and orthophotos characterized by sub-meter spatial resolution and time schedule suitable for monitoring the morphological evolution of the surface during the quiescent phases. During the last two effusive eruptions (2002-2003 and 2007) the surface modifications, suffered by the Sciara del Fuoco slope and by the crater area as a consequence of effusive activity, were quantified and controlled using the same methodologies. This work is mainly focused on the 2007 eruption but also accounts for analogies and differences with the 2002-2003 event being based on a multi-temporal quantitative analysis of the data collected from 2001 to 2007. The 2007 eruption involved the Sciara del Fuoco slope from the 27th February until the 2nd April: five flows produced a compound lava field including a lava delta on the shoreline and discharging most of the lava into the sea. The comparison of the 2007 DEMs with a pre-eruption surface (2006 LIDAR survey) allowed evaluating the total lava volume emplaced on the slope while two syn-eruption DEMs were used to calculate the average effusion rates through the eruption. Finally hypothesis on the lava discharge and slope instability mechanisms, which appear strongly connected, are formulated.
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Laser Scanning
Effusive eruption
Volcanology
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