eprintid: 1394
rev_number: 15
eprint_status: archive
userid: 2
dir: disk0/00/00/13/94
datestamp: 2015-03-02 07:38:34
lastmod: 2015-09-18 11:44:41
status_changed: 2015-04-27 12:10:49
type: thesis
metadata_visibility: show
creators_name: Nuannin, Paiboon
title: The Potential of b-value Variations as Earthquake Precursors for Small and Large Events
ispublished: pub
subjects: SS
divisions: EPOS-P
full_text_status: none
keywords: frequency magnitude distribution, b-values, rockburst, Andaman-Sumatra region, Zinkgruvan mine
abstract: The potential of variations of b-values in the G-R relation, logN=a-bM as earthquake precursors for small events (rockbursts) in Zinkgruvan mine, Sweden and for tectonic (large) earthquakes in the Andaman-Sumatra region were investigated. The temporal frequency-magnitude distribution, b(t), of rockbursts in Zinkgruvan mine was examined using high quality data recorded during the period November 1996 to April 2004 with magnitude ranges from Mw= -2.4 to 2.6. A sliding time-window was applied to compute b-values. The windows contain 50 events and were shifted with steps of 5 events. The results indicated that b-values significantly drop preceding rockbursts of magnitude Mw ≥ 1.6.Temporal and spatial variations of b-values were also examined for tectonic earthquakes, magnitude Mw ≥ 4.1, in the Andaman-Sumatra region. Earthquake data from the ISC, IDC, NEIC and HVRD earthquake catalogs for a period from 01/01/1995 to 12/26/2004 were used for analysis. Spatial variations of b were calculated from circular areas containing 50 events, with nodes on a 0.5° x 0.5° grid. The analysis shows that b(t) estimates using data from different catalogs are comparable and that large earthquakes are preceded by a drop in b(t) of about 0.3 ~ 1. The distribution of stress deduced from b-value mapping shows that large earthquakes occurred in the high stress, i.e. low b-value, areas.Aftershock sequences of the Mw=9, December 26, 2004 and the Mw=8.7, March 28, 2005 shocks were investigated by using the same methods. Results from aftershock sequences show similar behaviour as for the large and presumed independent main events.The observed variations of b-values with time and in space support the hypothesis that b-values have a precursory potential. The method can be used for a wide range of earthquake magnitude, from microearthquakes (Mw < 3) to giant tectonic shocks (Mw ~ 9) and for both of independent shocks and aftershocks.
date: 2006
date_type: published
institution: Uppsala University, SE-75236, Uppsala, Sweden
department: Department of Earth Sciences
thesis_type: phd
thesis_name: phd
access_IS-EPOS: limited
citation:   Nuannin, Paiboon  (2006) The Potential of b-value Variations as Earthquake Precursors for Small and Large Events.  PhD thesis, Uppsala University, SE-75236, Uppsala, Sweden.