Triggered earthquake study in Tranh River No. 2 (Vietnam) Hydropower Reservoir

This article presents the results of investigating triggered earthquakes in the vicinity of Tranh River No.2 Hydropower Reservoir in recent years. It is found that earthquakes occurred in the vicinity of Tranh River Hydropower Reservoir, probably associated with the Trà My — Trà BÓng fault zone. It is estimated that this fault is capable of hosting an earthquake of M~6.1. The ‘b’ value for this earthquake sequence is 0.83, which is higher than the regional ‘b’ value of 0.60. We estimate that the return period of earthquakes of M=4.5, 5.0, 5.5 and 6.0 is 11, 29, 76 and 198 months respectively. On October 22, 2012 an earthquake M_S=4.6, I₀=6.0 (MSK-64) occurred at 13:41:28 hrs GMT. The epicenter of the earthquake was located at a distance of 5.5 km away from the center of the dam towards the west. The focal depth is about 4.5 km, and the rupture length is about 1.8 km.     

Holocene estuarine sediments as a source of arsenic in Pleistocene groundwater in suburbs of Hanoi,Vietnam

Groundwater pollution by arsenic is a major health threat in suburban areas of Hanoi, Vietnam. The present study evaluates the effect of the sedimentary environments of the Pleistocene and Holocene deposits, and the recharge systems, on the groundwater arsenic pollution in Hanoi suburbs distant from the Red River. At two study sites (Linh Dam and Tai Mo communes), undisturbed soil cores identified a Pleistocene confined aquifer (PCA) and Holocene unconfined aquifer (HUA) as major aquifers, and Holocene estuarine and deltaic sediments as an aquitard layer between the two aquifers. The Holocene estuarine sediments (approximately 25–40 m depth, 9.6–4.8 cal ka BP) contained notably high concentrations of arsenic and organic matter, both likely to have been accumulated by mangroves during the Holocene sea-level highstand. The pore waters in these particular sediments exhibited elevated levels of arsenic and dissolved organic carbon. Arsenic in groundwater was higher in the PCA (25–94 μg/L) than in the HUA (5.2–42 μg/L), in both the monitoring wells and neighboring household tubewells. Elevated arsenic concentration in the PCA groundwater was likely due to vertical infiltration through the arsenic-rich and organic-matter-rich overlying Holocene estuarine sediments, caused by massive groundwater abstraction from the PCA. Countermeasures to prevent arsenic pollution of the PCA groundwater may include seeking alternative water resources, reducing water consumption, and/or appropriate choice of aquifers for groundwater supply.     

情理整合视角下旅游者环境责任行为与 意愿悖离研究——基于Logistic-ISM模型

基于对岳麓山景区447位旅游者的实地调研,运用拓展的计划行为理论并结合Logistic回归模型,分析影响两者发生悖离的因素,并进一步利用ISM解释结构模型分析各因素之间的逻辑关系.从Logistic回归结果看,旅游者的行为态度、感知行为控制等相关理性认知越好,发生悖离的可能性越低;旅游者积极环境情感和消极环境情感对悖离...