1. Investigating earthquakes nucleation from the resposne of Himalayan seismicity to the Monsoon Thomas ADER, Kristel Chanard Nadia LAPUSTA, and Jean-Philippe AVOUAC December 9, 2011

2. Secular/constant loading rate Sudden stress change due to a main earthquake: mainshock/aftershock sequences Here: periodic stresses on the Main Himalayan Fault, underneath Nepal. The study of earthquake triggering allows testing models of earthquake nucleation

3. TIBETINDIA GPS LOADING OF THE INDIAN PLATE DUE TO THE MONSOON NEPAL earthquakes

4. Modified from Bettinelli et al. (2008) GPS TIBETINDIA NEPAL TIBETINDIA NEPAL earthquakes

5. GPS S N Seismicity Montrer la serie GPS avec la prediction du modele de Kristel

6. Also periodic stress due to tides Coulomb stress 3kPatime 2 stresses with roughly the same amplitude (~3kPa) but different periods but… -No correlation of seismicity with tidal stress - Correlation with hydrological cycle (Monsoon)

7. Nucleation is time dependent. Nucleation predicted by rate-and-state friction on finite size faults can explain our observations The characteristic time for earthquake nucleation (hence faults frictional properties) can be assessed: – long enough so that the response to earth tides (12h) is damped – short that enough seismicity response to seasonal variations of stress. IMPLICATIONS FOR NUCLEATION