Asperity interaction and dependence of frequency-size distribution of
earthquakes in brittle-ductile transition zone in Central Himalaya
Abstract
We explore the hypothesis that b-value act as stress meter which varies
inversely with differential stress and decreases until it reached the
depth of brittle-ductile transition. Correlation of seismogenic asperity
and brittle-ductile contact (BDC) with b-value is of special interest.
Lowest b- and Dc-values coincides with transition depth and interpreted
as seismogenic asperities. Moderate ruptures (ML≥5.0) nucleate in
vicinity of transition zone where stress concentration is highest. We
illustrate behavior of mid-crustal detachment and dependence of
topographic elevation above Mid-Crustal Ramp (MCR). The depth 10-15 km
is marked as MCR which coincides with fluids, seismogenic asperity and
shows seismic clustering. The composite trend in abrupt escalation of
b-value is observed at depth ≈12 km and ≈7 km for Garhwal and Kumaun
region respectively. These depth ranges is demarcated as BDC which
coincides with proposed MCR and exhibiting as an alarming asperity zone
(12-15 km) for future great earthquake in Garhwal-Himalaya.