scholarly journals InSAR Coherence and Backscatter Images Based Analysis for the Anak Krakatau Volcano Eruption

Proceedings ◽  
2019 ◽  
Vol 24 (1) ◽  
pp. 21
Author(s):  
Arun Babu ◽  
Shashi Kumar
Keyword(s):  
Volcanic Eruption ◽  
Ocean Waves ◽  
Loss Of Life ◽  
Volcano Eruption ◽  
Tidal Waves ◽  
Before And After ◽  
Color Composite ◽  
Interferometric Sar ◽  
Krakatau Volcano ◽  
True Color

The Anak Krakatau Island and volcano caldera are located at the Sunda Strait between the Java and Sumatra Islands of Indonesia. The volcano started erupting on 22 December 2018, and collapse of the volcano resulted in Tsunami. The large tidal waves caused mass destruction and loss of life in the Java and Sumatra islands. The objective of this study was the interferometric SAR coherence and backscatter images based analysis of Anak Krakatau Island using Sentinel-1 SAR data. Seven datasets of ESA’s Sentinel-1 C-band satellite acquired from 25 November 2018 to 24 January 2019 were used in this study. The InSAR RGB composite images were generated by stacking together the interferometric coherence magnitude images and the sigma nought backscatter images. Sentinel-2 true color composite (TCC) images before and after the volcanic eruption were used to verify the results obtained through InSAR coherence analysis. The sigma nought backscatter image of 22 December 2018 clearly indicates the volcano eruption center and the ocean waves moving away from Anak Krakatau due to the seismic shock waves caused by the volcano eruption. The combined interpretation of the results revealed that the severe volcanic eruption on 22 December 2018 caused a large portion of the volcano to collapse, and all the rock debris which submerged to the ocean displaced the ocean water and resulted in the Tsunami at the Indonesian islands.

scholarly journals DETECTING THE AFFECTED AREAS OF MOUNT SINABUNG ERUPTION USING LANDSAT 8 IMAGERIES BASED ON REFLECTANCE CHANGE

2017 ◽  
Vol 12 (1) ◽  
pp. 49
Author(s):  
. Suwarsono ◽  
. Hidayat ◽  
Jalu Tejo Nugroho ◽  
. Wiweka ◽  
. Parwati ◽  
...  
Keyword(s):  
Volcanic Eruption ◽  
Threshold Value ◽  
The State ◽  
Single Band ◽  
Landsat 8 ◽  
Landsat 8 Oli ◽  
Volcano Eruption ◽  
Optical Images ◽  
Before And After ◽  
Reflectance Change

The position of Indonesia as part of a "ring of fire" bringing the consequence that the life of the nation and the state will also be influenced by volcanism. Therefore, it is necessary to map rapidly the affected areas of a volcano eruption. Objective of the research is to detect the affected areas of Mount Sinabung eruption recently in North Sumatera by using optical images Landsat 8 Operational Land Imager (OLI). A pair of Landsat 8 images in 2013 and 2014, period before and after eruption, was used to analysis the reflectance change from that period. Affected areas of eruption was separated based on threshold value of reflectance change. The research showed that the affected areas of Mount Sinabung eruption can be detected and separated by using Landsat 8 OLI images based on the change of reflectance value band 4, 5 and NDVI. Band 5 showed  the highest values of decreasing and band 4 showed the highest values of increasing. Compared with another uses of single band, the combination of both bands (NDVI) give the best result for detecting the affected areas of  volcanic eruption.

scholarly journals VOLCANIC ERUPTION-INDUCED TSUNAMI AT ANAK KRAKATAU VOLCANO, SUNDA STRAIT, INDONESIA

2020 ◽  
pp. 33
Author(s):  
Kaori Nagai ◽  
Taro Arikawa ◽  
Kwanchai Pakoksung ◽  
Fumihiko Imamura ◽  
Masashi Watanabe ◽  
...  
Keyword(s):  
Coastal Area ◽  
Volcanic Eruption ◽  
Run Up ◽  
Krakatau Volcano

On 22 December 2018, a volcanic eruption occurred at Anak Krakatau, Sunda Strait, Indonesia, which induced a tsunami. At the coastal area in the Sunda Strait, the destructive tsunami destroyed many structures and killed more than 400 people approximately 30 to 40 min after the eruption. In this event, it has been reported that many residents start to evacuate after seeing tsunami because alert of tsunami was not occurred. It is difficult to escape from a tsunami after seeing it waves, so early evacuation become important. Previously, many studies which handle Krakatau volcanic eruption induced tsunamis have been conducted. Pakoksung et al. (2019) conducted its simulation, but it was reported that the observed run-up heights and inundation depths were underestimated. Moreover, there were few studies which handle evacuation from non- seismic tsunami. The purpose of the study is to reveal the actual evacuation action from the tsunami induced by the 2018 volcanic eruption.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/ELOif7G4eNo

scholarly journals Krakatau caldera deposits: revisited and verification by geophysical means

2014 ◽  
Vol 57 (5) ◽  
Author(s):  
Izumi Yokoyama
Keyword(s):  
Wave Attenuation ◽  
Gravity Anomalies ◽  
Spatial Distributions ◽  
Low Density ◽  
Subsurface Structure ◽  
Font Size ◽  
S Wave ◽  
Before And After ◽  
Quantitative Examination ◽  
Krakatau Volcano

<p> </p><p>One of the differences between volcanic craters and calderas is that the latter bottoms are flatways filled with caldera deposit with lower density in comparison to country rocks. The 1883 Krakatau eruption affords us important knowledge on caldera formation even if it was not observed with modern sophisticated instruments. First, volcanic activities of the Krakatau Islands before and after the 1883 eruption are reexamined: previous suppositions involving a caldera-forming eruption of the proto-Krakatau prior to 1883 proved to be unsupported by the bathymetric topographies and gravity anomalies on and around the Krakatau Islands. Then, Anak Krakatau is interpreted as a parasitic cone of the main Krakatau volcano. As supplementary knowledge to discussion of caldera deposits, the results of drillings at several calderas in Japan and Mexico are introduced. Mass deficiency of the caldera deposit at Krakatau caldera is estimated by the gravity anomaly observed there and converted to probable volume with suitable density. For quantitative examination of the subsurface structure beneath the Krakatau complex, spatial distributions of seismic S-wave attenuation and Vp/Vs ratios have been already studied by temporary seismological observations and their results have been published. The high ratios of Vp/Vs observed approximately at Krakatau caldera may be attributable to the caldera deposit that is low density and contain much water. As additional remarks, a zone having both the characters, S-wave attenuation and zones of relatively high Vp/Vs ratio, may be a probable magma reservoir centering at a depth of about 10 km.</p><p><span style="font-size: 12.000000pt; font-family: 'TimesNewRomanPSMT';"><br /></span></p>

Tsunamis

2017 ◽  
Author(s):  
John A. Adam
Keyword(s):  
Mathematical Model ◽  
Large Scale ◽  
Volcanic Eruptions ◽  
Ocean Waves ◽  
The Other ◽  
Tsunami Generation ◽  
Sea Waves ◽  
Tsunami Propagation ◽  
Tidal Waves ◽  
Special Cases

This chapter describes a mathematical model of tsunami propagation (transient waves). A tsunami is a series of ocean waves triggered by large-scale disturbances of the ocean, including earthquakes, as well as landslides, volcanic eruptions, and meteorites. Tsunamis have very long wavelengths (typically hundreds of kilometers). They have also been called “tidal waves” or “seismic sea waves,” but both terms are misleading. The chapter first considers the boundary-value problem before modeling two special cases of tsunami generation, one due to an initial displacement on the free surface and the other due to tilting of the seafloor. It also discusses surface waves on deep water and how fast the wave energy propagates and concludes with an analysis of leading waves due to a transient disturbance.

scholarly journals AN ANALYSIS OF IMAGES BEFORE COMPRESSION IN PNG FORMAT

2010 ◽  
pp. 192-204
Author(s):  
Alexander Shport'ko
Keyword(s):  
Image Analysis ◽  
Dynamic Programming ◽  
Programming Language ◽  
C Programming Language ◽  
C Programming ◽  
Before And After ◽  
Continuous Tone ◽  
Minimum Block ◽  
Image Set ◽  
True Color

An influence of predictor’s different variants and their combination on PNG image compression is examined in this article. Fragments in C programming language for estimation of pixel lines entropy before and after application of context-dependent algorithm have been presented. A method for image analysis before the compression through breakdown of pixel lines with close entropy values into minimum blocks is offered. The method is based on the choice of an effective compression variant from five possible ones for every minimum block using dynamic programming and on the combination of contiguous minimum blocks in the homogeneous blocks of lines and on adjustment of their code parameters. It is experimentally showed that the images analysis, for example, allows to decrease the continuous tone images compression aspect of Kodak True Color PNG format image set on the average up to 12,37 bpp.

Time-dependent Tsunami Source Following the 2018 Anak Krakatau Volcano Eruption Inferred from Nearby Tsunami Recordings

2020 ◽  
Author(s):  
Yifan Zhu ◽  
Chao An ◽  
Teng Wang ◽  
Hua Liu
Keyword(s):  
Source Region ◽  
Time Dependent ◽  
Tsunami Source ◽  
Water Volume ◽  
Generation Process ◽  
Tsunami Generation ◽  
Time Duration ◽  
Initial Water ◽  
Volcano Eruption ◽  
Krakatau Volcano

Abstract The eruption of the Anak Krakatau volcano, Indonesia, on 22 December 2018 induced a destructive tsunami (the Sunda Strait tsunami), which was recorded by four nearby tidal gauges. In this study we invert the tsunami records and recover the tsunami generation process. Two tsunami sources are obtained, a static one of instant initial water elevation and a time-dependent one accounting for the continuous evolution of water height. The time-dependent results are found to reproduce the tsunami recordings more satisfactorily. The complete tsunami generation process lasts approximately 9 min and features a two-stage evolution with similar intensity. Each stage lasts about 3.5 min and elevates a water volume of about 0.15 km 3 . The time, duration and volume of the volcano eruption in general agree with seismic records and geomorphological interpretations. We also test different sizes of the potential source region, which lead to different maximum wave height in the source area, but all the results of time-dependent tsunami sources show the robust feature of two stages of wave generation. Our results imply a time-dependent and complex process of tsunami generation during the volcano eruption.

Development and Sea Test Results of a Deep-Sea Tsunami Warning Buoy System

2019 ◽  
Vol 53 (3) ◽  
pp. 6-15
Author(s):  
Yi Zhang ◽  
Hongmei Shang ◽  
Xiaojuan Zhang ◽  
Wei Ren
Keyword(s):  
Deep Sea ◽  
Water Pressure ◽  
Ocean Waves ◽  
Tsunami Warning ◽  
False Alarms ◽  
Underwater Acoustic Communications ◽  
Test Results ◽  
Tsunami Waves ◽  
Tidal Waves ◽  
Tsunami Detection

AbstractTsunamis are catastrophic ocean waves that could cause devastating damage to human lives, properties, and coastal infrastructures. This article presents the design and sea test results of a deep-sea tsunami warning buoy system. The system consists of a seafloor tsunami detection subsystem and a surface buoy. The tsunami detection subsystem monitors the tsunami waves through seafloor water pressure measurement. Detection of tsunami waves is achieved by separating the influence of astronomical tidal waves from the seafloor measurements via a cubic polynomial extrapolation method. The deep seafloor measurements and the tsunami detection results are transmitted in real time from the seafloor subsystem to the surface buoy via underwater acoustic communications; the buoy then relays the data to an onshore tsunami warning center via satellite links. The tsunami warning buoy system was evaluated in four deep-sea tests at different locations. In the last sea test, the system achieved an effective working duration of 108 consecutive days. This article analyzes the causes of false alarms and data transmission failures in the sea tests and puts forward effective solutions for system improvement. The system design and the sea test results could serve as references for future development of deep-sea infrastructures.

Age Determination of the Kawagodaira Volcanic Eruption in Japan by 14C Wiggle-Matching

Radiocarbon ◽  
2013 ◽  
Vol 55 (2) ◽  
pp. 748-752 ◽  
Author(s):  
Sayaka Tani ◽  
Hiroyuki Kitagawa ◽  
Wan Hong ◽  
Jung Hun Park ◽  
Ki Suk Sung ◽  
...  
Keyword(s):  
Confidence Level ◽  
Volcanic Eruption ◽  
Age Determination ◽  
Japanese Cedar ◽  
Central Japan ◽  
Volcano Eruption ◽  
Izu Peninsula ◽  
Pumice Flow ◽  
Eruption Age

The Kawagodaira Volcano is located on the northwest slope of Amagi Volcano on the Izu Peninsula of central Japan. The fine pumice that erupted from Kawagodaira Volcano is widely distributed in the central and western parts of the Japanese mainland. Here, we report an accurate eruption age determined by radiocarbon wiggle-matching of a Japanese cedar timber excavated from the pyroclastic deposit at the pumice flow terminal of Kawagodaira Volcano. The 14C wiggle-match estimate for the Kawagodaira Volcano eruption is 1210–1187 cal BC (95.4% confidence level).

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