Validation of an Index for Susceptibility to Earthquake-Induced Landslides Derived from Helicopter-Borne Electromagnetic Resistivity and Digital Elevation Data

Catastrophic earthquake-induced landslides can occur on slopes composed of loosened and fractured rock masses. Although it is impossible to prevent such landslides, estimation of the susceptibility of slopes to earthquake-induced landslides is useful for risk management. An index of susceptibility to earthquake-induced landslides (ISEL) was developed by using helicopter-borne electromagnetic resistivity data. However, the ISEL has not yet been validated through the analysis of pre-earthquake data. In this study, ISEL values were estimated from resistivity and digital elevation data obtained in 2013 around Mt. Aso, Kyushu, before the 2016 Kumamoto earthquake. Although most of the landslides around Mt. Aso during the 2016 Kumamoto earthquake were mass movements of volcanic tephra layers, some of them occurred on loosened rock masses. Landslide susceptible areas at loosened rock masses are the target for ISEL value estimation. Our results validated the effectiveness of the ISEL as a predictor of earthquake-induced rock mass landslides

Analysis of the Actions and Motivations of a Community during the 2017 Torrential Rains in Northern Kyushu, Japan

Damage caused by weather events has increased dramatically across the world in recent years. In the case of Japan, record-breaking rainfall has caused devastating damage almost every year since 2014; many people have been killed in these disasters. To better prepare for future heavy rainfalls, we need to discover how to prepare for disasters and mitigate damage by learning from examples in resilient communities. In 2017, torrential rains hit Toho Village in northern Kyushu, and the people as a whole responded well to avoid disastrous outcomes. We studied the actions and motivations of residents of Toho during this rainfall event by conducting semi-structured interviews in November 2017. The interviewees indicated that their motivation for evacuating was “personal observation of the danger” or “communication with neighbors”. Communication within the community was found to be an important factor that enabled the safe evacuation of community members, even without notice of the disaster risk and/or in the absence of timely information from the government because of a power outage. Knowledge of local landforms would be also helpful to reinforce appropriate actions and precautions needed during a disaster

Field experiment on flow-induced destruction of thermocline in a eutrophic reservoir

Oxygen levels in eutrophic water bodies can become rapidly depleted at the presence of stable thermal stratification. The anoxic condition induces the release of nutrients and heavy metals from bottom sediments, leading to water quality problems. In Goten reservoir, we installed two sets of jet flow generator. One jet flow generator transports the water near free surface and eject it near the bottom while the other discharges pumped groundwater near the bottom. Field measurement has been carried out to understand the destratification process by the induced flow and the resultant changes in water quality. It is demonstrated that the jet flow generators accelerate the destratification process considerably and that the spatial distribution of water quality in a horizontal plane shows little difference during the process. It is also found that further improvement with the jet flow generators is necessary to increase more effectively the dissolved oxygen concentration near the bottom

Field experiment on hypolimnic aeration using micro oxygen bubbles in a eutrophic reservoir

An in-situ experiment on hypolimnic aeration was carried out in Fuchu reservoir, which has been suffering from severe eutrophication, from mid-August to early December in 2004. Micro oxygen bubbles were injected into the anaerobic hypolimnion to improve water quality without disturbing the thermal stratification. Before the destratification due to big typhoons in the late September, some fundamental information was obtained which is useful in designing and maintaining an aeration system applied to eutrophic reservoirs. The operation of the micro-bubble aeration system increased the dissolved oxygen concentration to 1～3mg/L together with the decrease in electric conductivity, but within a limited area. This was explained by the very high consumption rate of dissolved oxygen in hypolimnic water and by bed materials. And the necessity was recognized to prevent the aerator nozzles from clogging accompanied by the oxidation of dissolved iron

Time-Series Remote Sensing Study to Detect Surface Water Seasonality and Local Water Management at Upper Reaches of Southwestern Bengal Delta from 1972 to 2020

Bengal delta experiences immense seasonality of surface water due to its geographical position. This study aims to explore the extent and seasonality of surface water in the southwestern part of Bangladesh (SWB) where human intervention has been rapidly changing the land use for several decades. This explorative study relied on a total of 312 high-resolution Landsat images from 1972 to 2020 and interviews to present crucial months, seasons, and periods for surface water in SWB. The study uses a valid threshold point ‘0′ for Normalized Difference Water Index (NDWI) to extract water pixels and confirms that the NIR band has better efficacy to separate water pixels. On average, the SWB has faced around 5.5% of surface water between 1972–2001, which increased to 12.8% between 2002 and 2020. Based on the median value, around 6% of surface water was observed in the 1990s, which increased to 16% in the 2010s. The average surface water was detected around 6% and 7% in December and January between 1972 and 2001, which expanded to 18% and 19% between 2002 and 2020, mainly because of human interventions such as mix-cropping. The study strongly suggests considering December and January months for further land use and land class studies which focus on the southwestern part of Bangladesh

Validation of an Index for Susceptibility to Earthquake-Induced Landslides Derived from Helicopter-Borne Electromagnetic Resistivity and Digital Elevation Data

Catastrophic earthquake-induced landslides can occur on slopes composed of loosened and fractured rock masses. Although it is impossible to prevent such landslides, estimation of the susceptibility of slopes to earthquake-induced landslides is useful for risk management. An index of susceptibility to earthquake-induced landslides (ISEL) was developed by using helicopter-borne electromagnetic resistivity data. However, the ISEL has not yet been validated through the analysis of pre-earthquake data. In this study, ISEL values were estimated from resistivity and digital elevation data obtained in 2013 around Mt. Aso, Kyushu, before the 2016 Kumamoto earthquake. Although most of the landslides around Mt. Aso during the 2016 Kumamoto earthquake were mass movements of volcanic tephra layers, some of them occurred on loosened rock masses. Landslide susceptible areas at loosened rock masses are the target for ISEL value estimation. Our results validated the effectiveness of the ISEL as a predictor of earthquake-induced rock mass landslides

The Association of Prenatal Exposure to Perfluorinated Chemicals with Glucocorticoid and Androgenic Hormones in Cord Blood Samples : The Hokkaido Study

Background: Perfluorinated chemicals (PFCs) disrupt cholesterol homeostasis. All steroid hormones are derived from cholesterol, and steroid hormones such as glucocorticoids and androgenic hormones mediate several vital physiologic functions. However, the in utero effects of PFCs exposure on the homeostasis of these steroid hormones are not well understood in humans. Objectives: We examined the relationship between prenatal exposure to perfluorooctane sulfonate (PFOS)/perfluorooctanoate (PFOA) and cord blood levels of glucocorticoid and androgenic hormones. Methods: We conducted a hospital-based birth cohort study between July 2002 and October 2005 in Sapporo, Japan (n = 514). In total, 185 mother-infant pairs were included in the present study. Prenatal PFOS and PFOA levels in maternal serum samples were measured using liquid chromatography-tandem mass spectrometry (LC-MS-MS). Cord blood levels of glucocorticoid (cortisol and cortisone) and androgenic hormones [dehydroepiandrosterone (DHEA) and androstenedione] were also measured in the same way. Results: We found a dose-response relationship of prenatal PFOS, but not PFOA, exposure with glucocorticoid levels after adjusting for potential confounders. Cortisol and cortisone concentrations were -23.98-ng/mL (95% CI: -0.47.12, -11.99; p for trend = 0.006) and -63.21-ng/mL (95% CI: -132.56, -26.72; p for trend < 0.001) lower, respectively, in infants with prenatal PFOS exposure in the fourth quartile compared with those in the first quartile. The highest quartile of prenatal PFOS exposure was positively associated with a 1.33-ng/mL higher DHEA level compared with the lowest quartile (95% CI: 0.17, 1.82; p for trend = 0.017), whereas PFOA showed a negative association with DHEA levels (quartile 4 vs. quartile 1: -1.23 ng/mL, 95% CI: -1.72, -0.25; p for trend = 0.004). We observed no significant association between PFCs and androstenedione levels. Conclusions: Our results indicate that prenatal exposure to PFCs is significantly associated with glucocorticoid and DHEA levels in cord blood