[M-GI34] Earth and planetary informatics with huge data management

[MGI34-10] Construction of hot spring database over Japan for clarifying thermal and fluid flow structures in the upper crust

*Jacek Scibek¹, Katsuaki Koike¹, Koki Kashiwaya¹ (1.Kyoto University)

Keywords:hot spring, database, geothermal, structures, heat flow

At Kyoto University, there is an on-going project that involves a review of various sources of geothermal data in Japan. The databases are updated using GIS, 3D models, and deep-learning algorithms to extract and correlated useful data. In the case of geothermal water use, the data exist in several categories that we must review and merge. One type of data are historical and modern records, maps, and statistics about the "hot spring" (thermal spring from warm to hot) development and management. Another important source of geothermal data are technical studies related to the geothermal energy exploration and development projects, but also in many of the managed hot spring areas, and natural volcanic areas. Finally, all data from deep drilling and studies are put together in a 3D hydro-structural-geothermal models and maps of heat flow and hydrothermal circulation and tectonic structure in Japan. This presentation is focused on the extraction of useful geothermal data for the national model from the observations of "hot springs" and thermally-heated groundwater anomalies in general. We are interested in the situation at the top of crystalline bedrock below surficial sediments and basins, although the hot and other springs usually emerge, or are pumped, within those shallow sediments because of the shallow depth (good access), and of high permeability and porosity (thermal water aquifers). These sediments usually obscure the true source of the thermal water up-flow location, but many fault zones are suspected to be sources in volcanic areas, and in some case, from deeper bedrock. There is some difficulty with understanding of some available data for many reasons: 1) commercial development (drilling, capturing, redistribution, etc.) of spring waters in Japan, 2) different definitions and labels used in geoscientific, local government statistics of "hot spring" use, and historical documents, 3) existing databases created for different purposes (e.g. whole hot spring areas vs. individual wells), 4) significant changes over the years of "hot spring" production and natural state. In our review in 2020, we noted that in many areas of Japan, almost the whole thermal plume in groundwater is captured and quantified, but in other areas only a small part of the thermal up-flow is used. Much of the thermal groundwater is lost to the hydrologic system or the ocean coast without counting the heat and mass flow. The improvement in these databases, and joining with other heat flow models (e.g. deep geothermal wells) can help to model the hydrothermal systems under Japan, and perhaps to also estimate the permeability of fault zone conduits and other conduits. Although the heat flow through rocks has been mapped regionally so far, the focus is also now on particular more permeable hot water conducting structures and the rates of heat flow through rocks and convectively by hot water circulation. The "hot spring" information is very abundant and is one of the best expressions of the underlying hydrothermal flow system and hydraulic structures under Japan. Therefore, these data and mappingresults can contribute to comprehensive understandings of the thermal fluid flow patters, geochemical water properties, and its relation with heat flow and geology within the upper Earth's Crust under Japan.