Imaging of a serpentinite complex in the Kamuikotan Zone, northern Japan, from magnetotelluric soundings

Ichihara, Hiroshi; Mogi, Toru; Uchida, Toshihiro; Satoh, Hideyuki; Yamaya, Yusuke; Fujii, Mahito; Yamazaki, Shusaku; Okazaki, Kenji; Tada, Norio

doi:10.1186/s40623-021-01482-5

Cited by 2 publications

References 44 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

A simple method to evaluate the uncertainty of magnetotelluric forward modeling for practical three-dimensional conductivity structure models

Baba

2023

Earth Planets Space

View full text Add to dashboard Cite

The forward calculation of magnetotelluric (MT) responses is generally assumed to be sufficiently accurate compared with typical observational errors in practical modeling and inversion studies. Although the uncertainty of the forward calculation may be examined by comparison with analytical or other numerical solutions for some simple models, such an examination does not guarantee that the uncertainty is similar for more realistic complex structures. In this study, I propose a simple method to evaluate the uncertainty of MT forward modeling for practical three-dimensional (3D) conductivity structure models in a Cartesian coordinate system. The method is based on the idea that the horizontal coordinate system can be selected arbitrarily for a general 3D structure. The synthesized MT responses are ideally identical irrespective of the selection but are different because of the difference in discretization angles, boundary values, and numerical errors. By synthesizing MT responses to the model in several different coordinate systems, the mean, standard deviation, and coefficient of variation can be calculated. These statistics provide quantitative information on how stably the forward calculations synthesize MT responses under the given conditions of the structure model, observation array, periods, numerical algorithm for the forward modeling, and mesh design. The proposed method was applied to two practical situations of seafloor MT arrays in the northwestern Pacific and southern Atlantic and a land MT array in Hokkaido, Japan. The results show that the uncertainty is comparable to real observation errors and is significantly dependent on the MT impedance element, period, site, structure model, and horizontal coordinate system. The uncertainty of the forward calculation should be considered for each element, period, and site to quantitatively evaluate how well a given model explains the data. I propose a new root-mean-square in which the residuals are normalized by both the standard errors of the MT responses observed and synthesized. This would help avoid overfitting data in the inversion analysis by ignoring the uncertainty of the forward calculation. This method is also useful for testing the appropriate selection of the coordinate system and mesh design. Graphical Abstract

show abstract

A simple method to evaluate the uncertainty of magnetotelluric forward modeling for practical three-dimensional conductivity structure models

Baba

2023

Earth Planets Space

View full text Add to dashboard Cite

show abstract

Geoelectrical evidence of fluid controlling slow and regular earthquakes along a plate interface

Nakamura,

Ichihara,

Goto

et al. 2024

Preprint

View full text Add to dashboard Cite

Shallow subducting plate interfaces, as sites of both destructive and “slow” earthquakes, resulting from rapid and slower fault slips, respectively, present a major scientific and disaster mitigation challenge. Although understanding the different slip mechanisms and their spatial relationships is critical, the role of a key factor, pore fluids, is understudied. Here we present clear observational evidence from Hyuga-nada, southwestern Japan, that the pore-fluid distribution correlates with fault rupture behavior. A 3D electrical resistivity model derived from marine magnetotelluric survey data reveals distinct resistive and conductive anomalies along the plate interface that reflect areas of scarce pore fluid and high concentration area of pore fluids sourced from subducting seamounts (Kyushu–Palau Ridge), respectively. The wet area corresponds to the slow slip area whereas dry and the transition areas correspond to areas of fast fault slip. These findings highlight the influence of the pore-fluid distribution on fault processes and underscore its importance in earthquake and tsunami risk assessments.

show abstract

Imaging of a serpentinite complex in the Kamuikotan Zone, northern Japan, from magnetotelluric soundings

Cited by 2 publications

References 44 publications

A simple method to evaluate the uncertainty of magnetotelluric forward modeling for practical three-dimensional conductivity structure models

A simple method to evaluate the uncertainty of magnetotelluric forward modeling for practical three-dimensional conductivity structure models

Geoelectrical evidence of fluid controlling slow and regular earthquakes along a plate interface

Contact Info

Product

Resources

About