Seismic and inter-seismic ground surface deformations of the Murono mud volcano (central Japan): a laser scanning approach

Abstract

A small mud volcano in Murono, Niigata Prefecture, north-central Japan, shows active ground surface displacements, not only when large earthquakes occur in the region but also during quiescent periods between earthquake events. The site recently underwent abrupt deformations due to strong regional earthquakes in 2004, 2007, 2011, and 2014, while gradual surface deformations were reported during quiescent periods between the earthquakes. To detect the spatial distribution of the changes in the mud volcano's ground surface elevation, we carried out multi-temporal terrestrial laser scanning. Point cloud datasets were registered at different times by minimizing the distance between the closest points in different clouds for stable ground features, which revealed centimeter-to decimeter-scale deformations around the domain of the conspicuous uplift. The spatial distribution of the deformation triggered by the earthquakes, including both central uplift and peripheral subsidence, exhibits an elliptical pattern, on which open crack fractures, associated with the earthquake-triggered uplift, were formed. The displacement and stress fields for the earthquakes were modeled numerically, and anomalously high pressure and/or weakening of the surficial materials was expected for the formation of fractures in the local domain. In contrast, continuous uplift was observed during the inter-seismic quiescent periods, the domain of which seems to have changed after the strong earthquake in 2014. In the coming years, further measurements will be necessary to unravel the physical subsurface mechanics of the mud volcano.

Preface to the special issue “High-definition topographic and geophysical data in geosciences”

“…Recent landscape changes can also be captured via high-definition platforms, such as TLS and UAS to produce new insights into landscape evolution in area experiencing seismic activity. TLS was used to detect subtle ground displacement at a centimeter scale in a mud volcano (Hayakawa et al 2017). An active mud volcano often reacts to a large seismic shake with its surface uplift, but the authors revealed that the mud volcano also actively "breathe" with frequent uplift and subsidence even when no shake is present in the region.…”