Estimation of Seismogenic Stress from the 2010 Darfield, 2011 Christchurch and 2016 Kaikoura, New Zealand Earthquakes and Implications for Strain Accumulation

Session: Crustal Stress and Strain and Implications for Fault Interaction and Slip [Poster]
Type: Poster
Date: 4/28/2020
Time: 08:00 AM
Room: Ballroom
Description: 

Despite the clear relationship between stress and earthquakes, knowledge of seismogenic stresses remains limited. The assumptions that slip during an earthquake will occur preferentially on a pre-existing fault plane rather than fracture intact rock and that slip occurs in the direction of maximum shear stress on the fault plane (the Wallace-Bott assumption), allow for the inference of seismogenic stresses from the coseismic slip rake, either from slickensides, focal mechanisms or finite slip models. With regards to the latter, we have previously shown that earthquakes rupturing several fault segments, with varied geometries and with varied direction of coseismic slip, are consistent with a homogenous state of stress along the entire fault zones immediately prior to nucleation. Here we estimate seismogenic stress tensors from coseismic slip models of the 2010 M_w7.1 Darfield, 2011 M_w6.3 Christchurch and 2016 M_w7.8 Kaikoura earthquakes in New Zealand. We invert published coseismic slip models using a Bayesian Markov Chain Monte Carlo strategy. Our preliminary results for the Kaikoura earthquake show a homogeneous stress with an EW trending, sub-horizontal most compressive stress direction and roughly NS trending and steeply plunging intermediate (plunging southward) and least (plunging northward) compressive stress directions. The coseismic slip models weakly constrain the stress magnitudes on their own, although there is a suggestion that the intermediate and least compressive stresses have similar magnitudes. We compare the seismogenic stresses from these three earthquakes, quantitatively testing whether the complex faulting patterns are indeed consistent with homogeneous seismogenic stresses. We also explore the relationships between the seismogenic stresses that led to the earthquakes and models of strain accumulation on the faults.

Presenting Author: Olivia L. Helprin

Authors