Upon the Hamadori earthquake（Mw 6.7）of 11 April 2011, coseismic surface deformation of 14 km running NNW to SSE in southeast Fukushima Prefecture occurred and was newly named the Shionohira Fault. However, no surface deformation was observed along the Kuruma Fault which is a southern extension of the Shionohira Fault. Fault injection tests using SIMFIP method at the Shionohira site on the former active segment and the Minakamikita site on the latter inactive segment were conducted to evaluate the activity of the two faults. Based on hydraulic responses to water injection into the fault rupture zone in the monitoring boreholes at the two sites, hydraulic properties of the area across the fault zone were estimated using the GRF model（Barker, 1988）. The results obtained on hydraulic conductivity, specific storage and flow dimension were consistent with those in the domestic and international literature. The hydraulic conductivity and specific storage were larger in Shionohira than in Minakamikita. The flow dimension of Shionohira was three-dimensional, while that of Minakamikita was found to be a two-dimensional fractional flow. In addition, it is understood that the volumetric expansion occurs in the former site in the triaxial direction and the latter in the uniaxial with the comparison between the uniaxial expansion coefficient calculated from the results of SIMFIP displacement measurements and the specific storage in the hydraulic analysis. The difference in the hydraulic parameters between the two sites corresponded to the difference in the spatial development of fractures considered to be the “water passway,” indicating the possibility of a correlation between the parameters and the different possible causes for fault activity at the two sites.

Heavy rainfall triggered by a quasi-stationary front occurred on 8-13 August 2022, leading to flooding of the Nakasato River in Tsugaru Plain, northern east Japan. Dike breaks along the river resulted in the deposition of a large amount of sediment, so-called crevasse-splay deposits, on the plain.

Crevasse splay deposits are mainly composed of fine to medium sand with gravels and can be divided into the following four units： Unit 1, gravel layer covering artificial soil layer; Unit 2, blue-grey fine sand; Unit 3 light brown medium to coarse sand and mud mixtures with mud clasts and gravel, indicating traction-carpet stratification; Unit 4 light yellow medium sand including erosional basal contact. The difference between four units correspond to the changes in flow condition during the flooding.

Sinusoidal tidal components in groundwater-level time series data collected from coastal aquifers affected by tide-level oscillations are used to determine aquifer hydraulic parameters through an analysis of the attenuation and delay during landward propagation. One method to determine the amplitude and initial phase of the sinusoidal tidal component, or to isolate the component from such groundwater observation data, is Fourier analysis. Two categories of errors are inevitable in the isolation of a sinusoidal component of a specific period from a finite-length time series using Fourier analysis. The errors are relevant to the component periods and the analyzed time series length. Therefore, appropriate selection of the analyzed time series length is essential to accurately isolate a tidal component from the observation time series data. This investigation addressed errors in the isolation of major tidal components, which have approximately diurnal or semidiurnal periods, from an artificial time series composed of the tidal components typical of coastal aquifers. The errors expected in isolation with analyzed lengths from one to one hundred days were investigated. The resultant outcome was an example selection of recommended time series lengths that should enable relatively accurate isolation of major tidal components by Fourier analysis.