Insights into earthquake source physics from high-frequency ... - IRIS

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Order of magnitude estimates with volumes For crack like ruptures, the moment scales T 3 with rupture size R as m 0 c* / V 1 0 ). / R The volume associated with the damage process can be written as V 2 = R 2 W with W = width of yielding zone From fracture mechanics, with stress intensity factor Thus W 2 0 K y K 0 ). 2 2 2 W 0 ). R /(. y (. 0) # R / S /(. (. ) R 0 2 and c ). m / d 0 S ) c . 0 2 S < 0.5 ! supershear rupture S > 1.5 ! subshear rupture If ). /. 0 0 0.1, ) c / c 0 0. 5 , and S = 0.5 (marginal supershear), m/d " 0.3 !!! If S = 1.5, 3 and 5 (subshear ruptures), m/d " 2.8, 11, and 31 !! If the modulus reduction is 25%, m/d " 5.6, 22, and 62 (still significant) ! Decomposition analysis: isotropic radiation from d # ) * ij c ijkl kl can be > DC component
Conclusions I • The ratio of radiation from the moment and damage-related processes scales as m / d 0 ( c / ) c )(). /. )( V 1 / V2 ) • Unless V 1 >> V 2 , u radiation. can be a significant component of the total • In fracturing of low porosity rocks and explosions, the radiation from the source to the bulk is larger than traditional estimates based only on the moment contribution. In fracturing of high porosity rocks involving compaction bands, the opposite is true. • Decomposition analysis suggests that the damage-related radiation can have a significant isotropic component. Much of the radiation of u damage is expected to be in high frequency waves. • Standard derivations of source parameters map erroneously the damagerelated radiation onto moment terms (slip and CLVD) • Reliable measurements of high frequency waves are needed to test the predictions associated with the damage-related radiation.
Page 1 and 2: Insights into earthquake source phy
Page 3 and 4: Basic relations Total strain has el
Page 5: Order of magnitude estimates of con
Page 9 and 10: Can be relevant to numerous importa
Page 11 and 12: Wrinkle-like rupture pulse complian
Page 13 and 14: Estimates of slip velocities (Ben-Z
Page 15 and 16: Slip-weakening friction (Shi and Be
Page 17 and 18: Simulations with imposed super-shea
Page 19 and 20: The results are robust with respect
Page 21 and 22: Relations to field observations? Ne
Page 23 and 24: Damage generation for different dep
Page 25 and 26: com. fracture length (cm) 60 50 40
Page 27 and 28: Scott et al. (1994) Shapiro et al.
Page 29 and 30: Pulverized rocks in the Mojave sect
Page 31 and 32: Asymmetric dynamic earthquake trigg
Page 33: Conclusions II • Ruptures along a

Insights into earthquake source physics from high-frequency ... - IRIS

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