Japan Geoscience Union Meeting 2022

Presentation information

[J] Oral

S (Solid Earth Sciences ) » S-TT Technology & Techniques

[S-TT40] Seismic Big Data Analysis Based on the State-of-the-Art of Bayesian Statistics

Sun. May 22, 2022 1:45 PM - 3:15 PM 301A (International Conference Hall, Makuhari Messe)

convener:Hiromichi Nagao(Earthquake Research Institute, The University of Tokyo), convener:Aitaro Kato(Earthquake Research Institute, the University of Tokyo), Keisuke Yano(The Institute of Statistical Mathematics), convener:Takahiro Shiina(National Institute of Advanced Industrial Science and Technology), Chairperson:Hiromichi Nagao(Earthquake Research Institute, The University of Tokyo), Aitaro Kato(Earthquake Research Institute, the University of Tokyo), Keisuke Yano(The Institute of Statistical Mathematics)

2:30 PM - 2:45 PM

[STT40-03] Estimation of Horizontal Velocity Fields from Euler Vector Inversion Using Gaussian Processes

*Tomohisa Okazaki1, Naonori Ueda1 (1.RIKEN Center for Advanced Intelligence Project)

Estimation of continuous horizontal velocity and strain-rate fields from discrete geodetic data is fundamental to understand crustal deformation. For this purpose, various interpolation methods have been proposed. Many methods interpolate 2-D velocity vectors in a relatively small area under a flat Earth approximation (Shen et al. 1996; Sandwell & Wessel 2016; Okazaki et al. 2021). Several methods properly take into account a spherical Earth: interpolation of 2-D velocity on a sphere (Tape et al. 2009); modeling of angular velocity (Euler vector) to obtain velocity fields (Ward 1998; Kreemer et al. 2018).

Following the last approach, this study formulates an inversion problem of angular velocity from velocity data. The inversion problem is solved by a vector-valued Gaussian process. To apply a Gaussian process, the covariance function of velocity is derived from that of angular velocity. Because a 3-D angular velocity is modeled from a 2-D horizontal velocity, the 3N×3N gram matrix of N data has rank 2N . This rank deficiency is a characteristic of the Euler vector inversion.

This method is applied to GNSS data in Japan during 2006–2009 (Okazaki et al. 2021). The results show a reasonable velocity field with small residuals. Angular velocity rapidly changes around Shikoku and the Bungo channel, which would correspond to a strong coupling between the Eurasian and Philippine sea plates. The estimated strain-rate fields show a large-scale variation, while lack a small-scale variation at volcanos found in Okazaki et al. (2021). Additionally, the estimated strain rate is higher along Fukui–Nagoya, which may be a plate boundary between the Eurasia and North American plates, than along Fukui-Kobe, which is a portion of the Niigata–Kobe tectonic zone. These results imply that the Euler vector inversion method mainly extracts crustal deformation caused by plate interactions.