GE 177 b I Introduction II Methods in

GE 177 b I. Introduction II. Methods in Morphotectonics III. Determining the time evolution of fault slip 1 - Techniques to monitor fault slip 2 - EQs phenomenology- Case studies 3 - EQs phenomenology- Scaling Laws 4 - Slow EQs phenomenology 5 - Paleoseismology 6 - Paleogeodesy Appendix: ‘Elastic Dislocation’ modeling

III. 2 -Earthquake Phenomenology • • The 2013 Balochistan EQ The 2015, Gorkha EQ The 1992, Landers EQ The 1999, Hector Mine EQ

The Mw= 7. 3, Landers earthquake 1992 (California),

Terminology, components and measurement of a slip vector

Yet, these measurements only give a ‘partial’ vision of the slip distribution on the rupture fault, for they only represent the (small? ) portion of the slip that has reached the surface. Mw=7. 1 Mw=7. 3 Mw=6. 5 Mw=7. 3 Besides, such complete measurements are quite rare and really reliable for strike slip faults only. Mw=7. 1 Mw=7. 6 (Manighetti et al, 2007)

Co-seismic displacement field due to the 1992, Landers EQ (based on Massonnet et al, Nature, 1993) G. Peltzer

Here the measured SAR interferogram is compared with a theoretical interferogram computed based on the field measurements of co-seismic slip using the elastic dislocation theory Co-seismic displacement field due to the 1992, Landers EQ This is a validation that coseismic deformation can be modelled acurately based on the elastic dislocation theory (based on Massonnet et al, Nature, 1993) G. Peltzer

• A common approach to investigate earthquake physics consists of producing kinematic source models from the inversion of seismic records jointly with geodetic data.

Kinematic Modeling of Earthquakes • Parameters to find out (assuming a propagating slip pulse) – Slip at each subfault on the fault – Rise time (the time that takes for slip to occur at each point on the fault). – Rupture velocity (how fast does the rupture propagate)

Landers (1992, Mw=7, 3) Hernandez et al. , J. Geophys. Res. , 1999

Sud Nord Joined inversion of geodetic, in. SAR data and seismic waveforms Hernandez et al. , J. Geophys. Res. , 1999

Sud Nord

Sud Hernandez et al. , J. Geophys. Res. , 1999 Nord

Observed and predicted waveforms Strong motion data Hernandez et al. , J. Geophys. Res. , 1999

(Bouchon et al. , 1997)

This analysis quantifies weakening during seismic sliding

Some characteristics of the Mw 7. 3 Landers EQ: • Rupture length: ~75 km • Maximum slip: ~ 6 m • Rupture duration: ~ 25 seconds • Rise time: 3 -6 seconds • Slip rate: 1 -2 m/s • Rupture velocity: ~ 3 km/s

– Seismic ruptures “pulse like” (e. g, Heaton, 1990) for large earthquakes (Mw>7) with rise times of the order of 3 -10 s typically – the rupture velocity is variable during the rupture but generally 0. 7 to 0. 9 the shear wave velocity. (2. 5 -3. 5 kms). It is occasionnally ‘supershear’ (>3. 5 -4 km/s). – Seismic sliding rate is generally of the order of 1 m/s – Large earthquakes typically ruptures faults down to 15 km within continent and down to 30 -40 km along subduction Zones. – Seismic ruptures are affected by fault geometries. They often stop at geometric complexities but can jump across significant stepovers – Slip variability measured at the small scale is probably due to off-fault anelastic defomation