An Analytic Study of Frictional Effect on Slip Pulses of Earthquakes

Jeen-Hwa Wang


Seismological observations show the existence of slip pulses with TR/TD<0.3, where TR and TD are, respectively, the rise time at a site on a fault and the duration time of ruptures over the fault. An analytical study of generation of a slip pulse is made based on the continuous form of 1-D spring-slider model, with uniform fault strengths, in the presence of linear, slip-weakening (SW) friction: f=1-u/D (u=the displacement and D=the characteristic distance) or linear, velocity-weakening (VW) friction: f=1-v/u (v=the velocity and u=the characteristic velocity). Let wo and tr are, respectively, the predominant angular frequency of the system and the arrival time at a site and define g=(1-1/D)1/2 and s=(1-1/4u2)1/2. There are complementary solution (CS), and particular solution (PS) of the equation of motion. The CS shows a slip pulse under some ranges of model parameters for SW friction and for VW friction when u>>1; while the CS shows a crack-like rupture for VW friction when u is not too large. For SW friction, TR and TR/TD decrease when the slip pulse propagates in advance along the fault and when wo and g increase. TR and TR/TD also depend on vR (rupture velocity) and increasing L (fault length). For the PS, Tp/TD is a good indication to show the existence of pulse-like oscillations at a site, because Tp (the predominant period of oscillations at a site) is slightly longer than TR. Results show the existence of a pulse-like oscillation at a site for the two types of friction. A pulse-like oscillation is generated when D>1.6 for SW friction and when u>0.6 for VW friction. Tp/TD decreases with increasing D. For the two types of friction, To/TD decreases when vR and L increase.


Slip pulse, pulse-like rupture, crack-like rupture, rise time, duration time, 1-D spring-slider model, slip-weakening friction, velocity-weakening friction

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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X