IASPEI - Picture Gallery

IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS008 Poster presentation 2016
Numerical modeling of self-potential variation associated with very longperiod
seismic pulse observed in the 2000 Miyake-jima volcanic activity
Mr. Osamu Kuwano
Shingo Yoshida, Masao Nakatani, Makoto Uyeshima
Transient self-potential (SP) variations were observed simultaneously with tilt-step events of the 2000
Miyake-jima volcano activities (Sasai et al. 2002). Very long-period seismic pulses (VLP pulses) with a
duration of about 50s (Ukawa et al., 2000; Fujita et al., 2002, 2004) were excited in these event. In this
study, we attempt to model the observed SP variation, assuming it was due to electrokinetic effect
accompanying fluid flow caused by VLP strain field. Though there have been many studies related to SP
variations due to electrokinetic phenomena accompanying crustal activities, most of them have aimed to
detect or evaluate static SP around faults or volcanoes. Few studies considered transient phenomena
(e.g., Pride et al., 2004). First, using Okadas (1992) program, strain field caused by VLP pulse was
calculated. Moment tensor of VLP pluses obtained by Kumagai et al. (2001) was used here. Fluid flow
was then obtained as poroelastic response. Then electric field at the surface was obtained by
integrating all streaming current sources induced by fluid flow. The simulation result agreed well with
observed SP variation, in terms of both amplitude and magnitude.
Keywords: electrokinetic