Detection of crustal inhomogeneity in the Nojima Fault zone using earth current noise

Authors
Citation
T. Hashimoto, Detection of crustal inhomogeneity in the Nojima Fault zone using earth current noise, ISL ARC, 10(3-4), 2001, pp. 306-317
Citations number
15
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Earth Sciences
Journal title
ISLAND ARC
ISSN journal
1038-4871 → ACNP
Volume
10
Issue
3-4
Year of publication
2001
Pages
306 - 317
Database
ISI
SICI code
1038-4871(200109/12)10:3-4<306:DOCIIT>2.0.ZU;2-B
Abstract
A resistivity survey method using artificial telluric noise was examined an d applied to a field of a fault zone. The electric earth current was measur ed at 50 sites in the Nojima Fault zone, which is in the northwestern part of Awaji Island, southwestern Japan. The dominant component of the observed electric field is supposed to be leakage currents from DC electric railway s running outside the island. Amplitude and polarization of the stray curre nt were systematically investigated and were revealed to represent the subs urface electrical structure of the study area. Some features on the fault z one's electrical structure have been pointed out, including: (i) an electri cal boundary that corresponds to a geological one between granite (resistiv e) and sediments (conductive); and (ii) a low resistivity spot on the surfa ce rupture of the earthquake fault. The structure estimated in the present study is both qualitatively and quantitatively consistent with previous res istivity surveys done using other methods pursued in the same area. It show s the validity of the 'stray current method' as one that is easy and uses l ow-cost resistivity exploration tools in a region where the effect of artif icial noise caused mainly by leakage currents from electrical railways cann ot be ignored.