GeoConnect³d introduced the concept of geomanifestations to define any distinct local expression of ongoing or past geological processes. These manifestations, or anomalies, often point to specific geologic conditions and, therefore, can be important sources of information to improve geological understanding of an area. Examples include seismicity, gas seeps, local compositional differences in groundwater and springs, thermal anomalies, mineral occurrences, jumps in hydraulic head, overpressured zones and geomorphological features. Geomanifestations are an addition to the structural framework model also being developed in GeoConnect³d, aiming to show where and how processes and structures may be linked. Data on geomanifestations are being collected in three areas: the Roer-to-Rhine area of interest in northwest Europe, and the Mura-Zala Basin and Battonya High within the Pannonian Basin area of interest in Eastern Europe. A first assessment of available data showed that groundwater-related geomanifestations in the form of anomalies in chemical composition (enrichment in elements such as Fe, or hydrocarbon gases and CO2,) or temperature (thermal water springs, geothermal anomaly in wells) are mappable in all areas. These geomanifestations point to special geological features in each area, such as proximity to magmatic reservoirs, presence of deep-rooted faults and considerable differences in the subsurface relief (trough–high system of the basement) among others. These anomalies at times define spatial patterns, which might or not be represented in the structural framework model, thus demonstrating whether they can be explained by the current geological understanding embedded in the structural framework. With this first test, we conclude that data on groundwater-related geomanifestations add to the robustness of the structural framework model. Further investigations with other types of geomanifestations are foreseen. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 731166.
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RBINS Staff Publications 2020
Within the framework of the QuakeRecNankai project, which focuses on the geological record of paleoearthquakes rupturing the Nankai-Suruga subduction zone, we sampled bottom sediments of the Fuji Five Lakes at the foot of Mount Fuji. In October 2014, we acquired 23 short gravity cores from Motosu, Sai, Kawaguchi and Yamanaka Lakes. We focus on investigating the sensitivity of each lake for recording natural hazards (storms, floods, volcanic eruptions, earthquakes). Recent natural hazards impacting the Fuji Five Lakes area are expected to be recorded as rapidly deposited layers within the background hemipelagic sediments. We seek to identify event deposits in the collected short cores based on visual identification combined with high resolution analyses, comprising geophysical and geochemical properties, grain size and X-ray images. We establish an age-depth model by combining radionuclide (14C,137Cs,210Pb) dating with the identification of historical tephra layers, in particular the one deposited during the Hoei eruption (AD 1707) of Mount Fuji. The sedimentary events in each lake are compared to a historical catalogue of natural hazards in the Fuji Five Lakes area, including historical records of megathrust earthquakes rupturing the Nankai subduction zone and other earthquakes occurring along the inland active faults that produced significant shaking (MKS intensity >7) in the Fuji Five Lakes area. The preliminary sedimentary study highlights the high sensitivity of Motosu Lake compared to the very shallow Yamanaka and Kawaguchi Lakes, which we attribute to its specific geomorphology. Motosu Lake is characterized by a deep basin, surrounded by very steep slopes. The generation of earthquake triggered mass transport deposits/turbidites and the preservation of the deposits are favored due to the architecture of the basin. The Fuji lake sensitivity to megathrust events will be the target of a future coring campaign to retrieve a longer geological record.
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