Variations in Apparent Stress and b Value Preceding the 2010 Mw8.8 Bio-Bío, Chile Earthquake

Abstract We calculated apparent stresses for 70 earthquakes ( M W ? 5.0) occurring in the aftershock region of 2010 8.8 Bio-Bío earthquake from January 1990 to September 2019. identified that average stress was approximately 0.487 MPa between and December 2005 1.063 within period 2006 2010. The latter one is 2.2-fold greater than former, representing a significant difference as determined by z test, with 99% confidence level. Moreover, we analyzed temporal evolution found rapidly increased 0.43 1.2 during pre-event March occurrence mainshock, this be at 98% Furthermore, spatial distribution study observed two higher-apparent-stress regions, which epicenter event located. On basis inverse correlation b value stress, values were compared those stress. comparison showed decreased 4 years before while substantially; lower , higher, vice versa. Therefore, supported results obtained present can probably considered precursors great earthquakes.