Simulation_Tohoku
A conceptual cycle simulation of the Tohoku-Oki earthquake. The megathrust event has a recurrence time of ~600 years, and the deep brittle asperities produce high-frequency contents during the megathrust event. These asperities also produce inter-megathrust M7 earthquakes recurring every several years.
The 2010 Tohoku Great Earthquake was a devastating disaster to all human beings. It features outstanding characters as huge slip (>50m) towards the trench and high frequency radiations from the deeper part of the subduction zone during the megathrust event (with a possible recurrence time of ~1000 years), and numbers of M7 earthquakes between megathrust events. Here we perform quasi-dynamic simulations trying to reproduce these key features.
To reduce computational cost, it will be wise to perform a multi-cycle simulation in a 2D simulation (i.e. single cell along-dip) first.
This model comes with a velocity-weakening zone between 10km to 32 km in depth, and the effective normal stress linearly increases from surface (the trench) to 20km deep, then remain constant. The whole fault has a Dc (characteristic slip distance) of 0.4m. This parameter combination yields a multi-cycle megathrust events with recurrence time of ~1000 years and huge slip toward trench.
Figure 1: Simulation of multiple subduction earthquake cycles in 2D:
(a) Assumed depth-dependent distribution of rate-and-state friction parameters (a-b) and effective normal stress (σ). (b) Evolution of cumulated slip over several earthquake cycles. Each curve shows the slip as a function of depth at a certain time. The time intervals are irregularly sampled and longer than dynamic rupture timescales. The widely spaced profiles correspond to megathrust earthquakes. (c) Evolution of slip during a megathrust earthquake. Same representation as in (b), but with shorter time intervals. (d) Moment rate as a function of time over 10 earthquake cycles.
This model comes with 11 brittle asperities randomly distributed at the deeper part of the subduction zone. The megathrust event has a recurrence time of ~600 years, and the deep brittle asperities produce high-frequency contains during the megathrust event. These asperities also produce inter-megathrust M7 earthquakes recurring every several years.
Figure 2: 3D simulation with deep brittle asperity:
Left panel: spatial distribution of logarithmic slip-rate normalized by plate velocity on the fault at selected time during and between two megathrust events. Snapshot times are indicated by red circles in the right panel. Right panel: Peak slip-rate as a function of time.
Animation: 3D simulation with deep brittle asperity:
The upper panel shows the logarithmic slip-rate normalized by the plate velocity. The lower panel shows the global peak slip-rate as a function of time, respectively.
[http://code.google.com/p/qdyn/downloads/detail?name=QDYN_DEMO_Tohoku_with_Results.zip Download Full DEMO Package w/ Result Matrix]
[http://code.google.com/p/qdyn/downloads/detail?name=QDYN_DEMO_Tohoku.zip Download DEMO Package w/o Result Matrix]