Research

Seafloor Massive Sulfide (SMS) Exploration

Next-generation metallic resources called seafloor massive sulfide deposits have been discovered in the seas around Japan. Since SMS deposits contain many metallic minerals that conduct electricity well, electrical and electromagnetic (EM) exploration — which can obtain information about subsurface electrical conductivity — is effective for mapping their distribution.

I have been applying electrical/EM exploration in the Iheya and Irabu hydrothermal fields in the Okinawa Trough to elucidate subsurface resistivity structures and the formation mechanisms of SMS deposits. In the Iheya field, as reported in Ishizu et al. (2019, GRL), new discoveries were made regarding the morphology and development mechanism of SMS deposits.

Geothermal Resource Exploration

I focus particularly on supercritical geothermal resources — fluids in a supercritical state that carry extremely high energy. Power generation using supercritical fluids is expected to achieve far greater output than conventional geothermal power using hydrothermal fluids below 350°C.

Using the magnetotelluric (MT) method, I have conducted EM surveys in the Yuzawa geothermal field (Akita Prefecture), retrieved 3D subsurface resistivity models, and combined them with temperature log data to elucidate the distribution and formation mechanisms of supercritical geothermal resources.

Volcanic Structure Exploration

I conduct research related to volcanoes, focusing on Kusatsu-Shirane Volcano. Phreatic eruptions have occurred here repeatedly since recorded history in 1805. Phreatic eruptions are caused by groundwater boiling due to heat indirectly delivered from magma, launching large ballistic projectiles. They are notoriously difficult to predict because precursory phenomena such as seismic activity are generally absent.

I am developing subsurface structure monitoring technology for predicting phreatic eruptions — elucidating eruption mechanisms and detecting spatiotemporal changes in subsurface resistivity to enable eruption prediction.

Development of EM Inversion Software

EM exploration involves recording electromagnetic field data at the surface or seafloor, then inverting the observed data to recover subsurface resistivity structures. Inversion discretizes the structure into ~100,000–1,000,000 model cells, making computational cost high.

I have developed computationally efficient inversion software using a “data-space transformation” approach, and also built flexible EM inversion software capable of handling data from various acquisition configurations beyond those supported by existing tools.