scholarly journals Land Cover Classification by Integrating NDVI Time Series and GIS Data to Evaluate Water Circulation in Aso Caldera, Japan

2020 ◽  
Vol 17 (18) ◽  
pp. 6605
Author(s):  
Hiroki Amano ◽  
Yoichiro Iwasaki
Keyword(s):  
Land Cover ◽  
Groundwater Recharge ◽  
Circulation Model ◽  
Water Circulation ◽  
2016 Kumamoto Earthquake ◽  
The 2016 Kumamoto Earthquake ◽  
Gis Data ◽  
Ndvi Time Series ◽  
Aso Caldera ◽  
Land Cover Maps

Grasslands in Aso caldera, Japan, are a type of land cover that is integral for biodiversity, tourist attractions, agriculture, and groundwater recharge. However, the area of grasslands has been decreasing in recent years as a result of natural disasters and changes in social conditions surrounding agriculture. The question of whether the decrease in spring water discharge in Aso caldera is related to the decrease in grasslands remains unanswered. To clarify this relationship, a water circulation model that considers land covers with different hydrological features is needed. In this study, by integrating Normalized Difference Vegetation Index (NDVI) time series and Geographic Information System (GIS) data, we generated land cover maps from the past (in 1981 and 1991) to the present (in 2015 and 2016), before and after the 2016 Kumamoto earthquake, and then for the future (in the 2040s); these maps formed the dataset for building a water circulation model. The results show that the area of grasslands, which are reported to have a higher groundwater recharge rate than that of forests, in 2016 had decreased to 68% of the area in 1981 as a result of afforestation and transformation into forests, as well as landslides induced by the earthquake. The area of grasslands is predicted to further drop to 60% by the 2040s. On the other hand, the area of forests (conifers and hardwoods) in 2016 had increased by 119% relative to that in 1981 because of the transformation of grasslands into forests, although these areas decreased as a result of landslides due to the 2016 Kumamoto earthquake. Quantification of groundwater recharge from grasslands and forests using the land cover maps generated for 1981, 1996, 2015, and 2016 shows that the annual increase in precipitation in these years significantly affected groundwater recharge; these effects were greater than those associated with the type of land cover. Thus, the groundwater recharge increased, despite the decrease in grasslands. However, when constant precipitation was assumed, the groundwater recharge presented a decreasing trend, indicating the importance of maintaining and conserving grasslands from the viewpoint of groundwater conservation.

EARTHFLOW DEPOSITS TRIGGERED BY THE 2016 KUMAMOTO EARTHQUAKE IN ASO CALDERA, SW JAPAN

2016 ◽  
Author(s):  
Mitsuru Okuno ◽  
◽  
Masayuki Torii ◽  
Ken-ichi Nishiyama ◽  
Toshimichi Nakanishi ◽  
...  
Keyword(s):  
2016 Kumamoto Earthquake ◽  
Kumamoto Earthquake ◽  
The 2016 Kumamoto Earthquake ◽  
Aso Caldera ◽  
Sw Japan

scholarly journals Postseismic Deformation Following the 2016 Kumamoto Earthquake Detected by ALOS-2/PALSAR-2

2020 ◽  
Author(s):  
Manabu Hashimoto
Keyword(s):  
Surface Deformation ◽  
Postseismic Deformation ◽  
Mountainous Area ◽  
2016 Kumamoto Earthquake ◽  
Ionospheric Correction ◽  
Kumamoto Earthquake ◽  
The 2016 Kumamoto Earthquake ◽  
Aso Caldera ◽  
Surface Ruptures ◽  
High Coherence

Abstract We have been conducting study of postseismic deformation following the 2016 Kumamoto earthquake using ALOS-2/PALSAR-2 acquired till 2018. We apply ionospheric correction to interferograms of ALOS-2/PALSAR-2. L-band SAR gives us high coherence enough to reveal surface deformation even in vegetated or mountainous area for pairs of images acquired more than 2 years. Ionospheric disturbances are seen both in the ascending and descending images, but spatial characteristics may be different each other. Postseismic deoformation following the Kumamoto earthquake is much larger than those observed after recent inland earthquakes in Japan with GPS, which exceeds 10 cm during two years at some spots in and around Kumamoto city and Aso caldera. There are sharp changes across several coseismic surface ruptures such as Futagawa, Hinagu and Idenokuchi faults. Time constant of postseismic decay ranges from 1 month to 600 days at selected points, but that LOS changes during the first epochs or two are dominant. This result suggests multiple source of postseismic deformation. LOS changes around the Hinagu and Suinzenji faults that appeared during the mainshock in Kumamoto City may be explained with right lateral afterslip on these faults. LOS changes around the Hinagu and Idenokuchi faults cannot be explained with right-lateral afterslip, which requires another unknown source. Deformation in northern part of Aso caldera may be the result of right lateral afterslip on unknown fault.

MECHANISM OF THE GRABENS THAT FORMED IN THE ASO CALDERA DURING THE 2016 KUMAMOTO EARTHQUAKE

2021 ◽  
Vol 21 (6) ◽  
pp. 6_31-6_56
Author(s):  
Susumu YASUDA ◽  
Naoto OHBO ◽  
Masanobu SHIMADA ◽  
Tatsuro CHIBA ◽  
Hideo NAGASE ◽  
...  
Keyword(s):  
2016 Kumamoto Earthquake ◽  
Kumamoto Earthquake ◽  
The 2016 Kumamoto Earthquake ◽  
Aso Caldera

scholarly journals Estimation of Groundwater Recharge in Kumamoto Area, Japan in 2016 by Mapping Land Cover Using GIS Data and SPOT 6/7 Satellite Images

2022 ◽  
Vol 14 (1) ◽  
pp. 545
Author(s):  
Hiroki Amano ◽  
Yoichiro Iwasaki
Keyword(s):  
Land Cover ◽  
Natural Disasters ◽  
Groundwater Recharge ◽  
Satellite Images ◽  
Sustainable Use ◽  
Paddy Fields ◽  
Fiscal Year ◽  
Domestic Water ◽  
Gis Data ◽  
Land Cover Map

Agricultural fields, grasslands, and forests are very important areas for groundwater recharge. However, these types of land cover in the Kumamoto area, Japan, were damaged by the Kumamoto earthquake and heavy rains in 2016. In this region, where groundwater provides almost 100% of the domestic water supply for a population of about 1 million, quantitative evaluation of changes in groundwater recharge due to land cover changes induced by natural disasters is important for the sustainable use of groundwater in the future. The objective of this study was to create a land cover map and estimate the groundwater recharge in 2016. Geographic information system (GIS) data and SPOT 6/7 satellite images were used to classify the Kumamoto area into nine categories. The maximum likelihood classifier of supervised classification was applied in ENVI 5.6. Eventually, the map was cleaned up with a 21 × 21 kernel filter, which is larger than the common size of 3 × 3. The created land cover map showed good performance of the larger filter size and sufficient validity, with overall accuracy of 91.7% and a kappa coefficient of 0.88. The estimated total groundwater recharge amount reached 757.56 million m3. However, if areas of paddy field, grassland, and forest had not been reduced due to the natural disasters, it is estimated that the total groundwater recharge amount would have been 759.86 million m3, meaning a decrease of 2.30 million m3 in total. The decrease of 2.13 million m3 in the paddy fields is temporary, because the paddy fields and irrigation channels have been improved and the recharge amount will recover. On the other hand, since the topsoil on the landslide scars will not recover easily in natural conditions, it is expected to take at least 100 years for the groundwater recharge to return to its original state. The recharge amount was estimated to decrease by 0.17 million m3 due to landslides. This amount is quite small compared to the total recharge amount. However, since the reduced recharge amount accounts for the annual water consumption for 1362 people, and 12.1% of the recharge decrease of 1.41 million m3 each year to fiscal year 2024 is expected by municipalities, we conclude that efforts should be made to compensate for the reduced amount due to the disasters.

Mechanism of the Grabens that formed in the Aso Caldera during the 2016 Kumamoto Earthquake

2021 ◽  
Vol 21 (1) ◽  
pp. 1_135-1_158
Author(s):  
Susumu YASUDA ◽  
Naoto OHBO ◽  
Masanobu SHIMADA ◽  
Tatsuro CHIBA ◽  
Hideo NAGASE ◽  
...  
Keyword(s):  
2016 Kumamoto Earthquake ◽  
Kumamoto Earthquake ◽  
The 2016 Kumamoto Earthquake ◽  
Aso Caldera

scholarly journals Postseismic Deformation Following the 2016 Kumamoto Earthquake Detected by ALOS-2/PALSAR-2

2020 ◽  
Author(s):  
Manabu Hashimoto
Keyword(s):  
Surface Deformation ◽  
Postseismic Deformation ◽  
Mountainous Area ◽  
2016 Kumamoto Earthquake ◽  
Ionospheric Correction ◽  
Kumamoto Earthquake ◽  
The 2016 Kumamoto Earthquake ◽  
Aso Caldera ◽  
Surface Ruptures ◽  
Buried Fault

Abstract I have been conducting a study of postseismic deformation following the 2016 Kumamoto earthquake using ALOS-2/PALSAR-2 acquired till 2018. I apply ionospheric correction to interferograms of ALOS-2/PALSAR-2. L-band SAR gives us high coherence enough to reveal surface deformation even in vegetated or mountainous area for pairs of images acquired more than 2 years. Postseismic deformation following the Kumamoto earthquake exceeds 10 cm during two years at some spots in and around Kumamoto city and Aso caldera. Westward motion of ~6 cm/yr was dominant on the southeast side of the Hinagu fault, while westward shift was detected on both side of the Futagawa fault. The area of latter deformation seems to have correlation with distribution of pyroclastic flow deposits. Significant uplift was found around the eastern Futagawa fault and on the southwestern frank of Aso caldera, whose rate reaches 4 cm/yr. There are sharp changes across several coseismic surface ruptures such as Futagawa, Hinagu, and Idenokuchi faults. Rapid subsidence between Futagawa and Idenokuchi faults also found. It is confirmed that local subsidence continued along the Suizenji fault, which newly appeared during the mainshock in Kumamoto City. Subsidence with westward shift of up to 4 cm/yr was also found in Aso caldera.Time constant of postseismic decay ranges from 1 month to 600 days at selected points, but that postseismic deformation during the first epochs or two are dominant at point in the Kumamoto Plain. This result suggests multiple source of deformation. Westward motion around the Hinagu fault may be explained with right lateral afterslip on the shallow part of this fault. Subsidence along the Suizenji fault can be attributed to normal faulting on dipping westward. Deformation around the Hinagu and Idenokuchi faults cannot be explained with right-lateral afterslip of Futagawa fault, which requires other sources. Deformation in northern part of Aso caldera might be the result of right lateral afterslip on a possible buried fault.

scholarly journals Postseismic Deformation Following the 2016 Kumamoto Earthquake Detected by ALOS-2/PALSAR-2

2020 ◽  
Author(s):  
Manabu Hashimoto
Keyword(s):  
Surface Deformation ◽  
Postseismic Deformation ◽  
Mountainous Area ◽  
2016 Kumamoto Earthquake ◽  
Ionospheric Correction ◽  
Kumamoto Earthquake ◽  
The 2016 Kumamoto Earthquake ◽  
Aso Caldera ◽  
Surface Ruptures ◽  
Buried Fault

Abstract I have been conducting a study of postseismic deformation following the 2016 Kumamoto earthquake using ALOS-2/PALSAR-2 acquired till 2018. I apply ionospheric correction to interferograms of ALOS-2/PALSAR-2. L-band SAR gives us high coherence enough to reveal surface deformation even in vegetated or mountainous area for pairs of images acquired more than 2 years. Postseismic deformation following the Kumamoto earthquake exceeds 10 cm during two years at some spots in and around Kumamoto city and Aso caldera. Westward motion of ~6 cm/yr was dominant on the southeast side of the Hinagu fault, while westward shift was detected on both side of the Futagawa fault. The area of latter deformation seems to have correlation with distribution of pyroclastic flow deposits. Significant uplift was found around the eastern Futagawa fault and on the southwestern frank of Aso caldera, whose rate reaches 4 cm/yr. There are sharp changes across several coseismic surface ruptures such as Futagawa, Hinagu, and Idenokuchi faults. Rapid subsidence between Futagawa and Idenokuchi faults also found. It is confirmed that local subsidence continued along the Suizenji fault, which newly appeared during the mainshock in Kumamoto City. Subsidence with westward shift of up to 4 cm/yr was also found in Aso caldera. Time constant of postseismic decay ranges from 1 month to 600 days at selected points, but that postseismic deformation during the first epochs or two are dominant at point in the Kumamoto Plain. This result suggests multiple source of deformation. Westward motion around the Hinagu fault may be explained with right lateral afterslip on the shallow part of this fault. Subsidence along the Suizenji fault can be attributed to normal faulting on dipping westward. Deformation around the Hinagu and Idenokuchi faults cannot be explained with right-lateral afterslip of Futagawa fault, which requires other sources. Deformation in northern part of Aso caldera might be the result of right lateral afterslip on a possible buried fault.

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