Huihui Weng
Associate Professor (tenure-track), Nanjing University, China
e-mail: weng@nju.edu.cn
Nanjing University Xianlin Campus, 163 Xianlin Road, Nanjing, China
The dynamics of long ruptures (slow slip events)
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The dynamics of long ruptures (dip-slip; subshear)
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The dynamics of long ruptures (strike-slip; supershear)
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The dynamics of long ruptures (mixed-mode; a continuum of speeds)
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Supershear transition induced by barriers
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Constraining frictional properties
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Damage fault zone increases earthquake size
The dynamics of long ruptures (slow slip events)
Slow slip events occur worldwide and could trigger devastating earthquakes, therefore geophysicists are particularly interested in understanding their fundamental mechanics and their relationship with the fast, damaging earthquakes. Yet it is still debated whether or not the empirical relation between the magnitude and duration is similar for slow slip events and regular earthquakes.
We found that the rupture propagation of both slow and fast earthquakes can be predicted by a new theory of dynamic fracture mechanics. This theory accounts for an essential ingredient that was missing in previous models and experiments, the “finite seismogenic depth”. The energy ratio between fracture energy and energy release rate controls the complete spectrum of rupture speeds from arbitrarily slow speeds up to the S-wave speed. We also managed to reconcile the debated scaling features of slow slip events by using this new theory.
Weng and Ampuero, Nat. Comm. 2022
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The dynamics of long ruptures (dip-slip; subshear)
How do ruptures propagate along strike? What controls the rupture speed and the final earthquake size?
The dynamics of ruptures in 3-D dynamic rupture simulations can be well described by the following inertial equation-of-motion:
New theory
The definition of a rupture potential based on the equation-of-motion can be used to assess the location of rupture arrest, similar to the gravity potential.
Gravity potential
Rupture potential
The rupture potential also helps conceptualize fault behavior during a sequence of multiple ruptures and earthquake cycles.
Weng and Ampuero, JGR, 2019
The dynamics of long ruptures (strike-slip; supershear)
How do supershear ruptures propagate along strike? What controls the supershear speed?
New theory
The new 3-D theoretical equation-of-motion predicts that the supershear ruptures can propagate steadily and their speeds are controlled by the energy ratio, validated by 3-D dynamic rupture simulations. Both the theory and the simulations predict that steady supershear ruptures are super-Eshelby (>1.414Vs).
Weng and Ampuero, in manuscript
The dynamics of long ruptures (mixed-mode; a continuum of speeds)
Previous analytical models determined a forbidden speed range situated between the speed of P and S waves. However, seismological observations demonstrate that recent earthquakes had actually propagated within the forbidden range, such as the 2018 Mw7.5 Palu earthquake. How can we reconcile the theories with the seismological observations?
Utilizing our new-developed 3D equation-of-motion of oblique slip, we were able to explain why the "forbidden speeds" are actually admissible.
New theory
What is the implication for physics-based seismic hazard assessment?
Weng and Ampuero, Nat Geo, 2020
Supershear transition induced by barriers
2D numerical simulations demonstrated that the barrier a stress heterogeneity with strong friction strength can induce transient supershear ruptures (rupture speed is faster than the shear wave speed) and thus aggravate near-field ground shaking.
Weng, Huang, and Yang, 2015
Constraining frictional properties
How can we constrain the frictional parameters on the fault?
By utilizing different trade-off patterns of source parameters and multiple observations for the first time, we can determine the frictional parameters of the seismogenic fault. The best fit dynamic model yields a Dc (slip-weakening distance) value of ~0.6 m, in contrast to the previous kinematical estimation of ~5 m.
Weng and Yang, 2018
Damage fault zone Increases earthquake size
How do damage fault zones affect rupture propagation?​
1. Damage fault zones could promote the rupture extents
2. The promotional effects increase with the width and depth extent of damage fault zones
3. Along-strike segmented fault zones may lead to preferred rupture directions
