TY - JOUR
T1 - Earthquake Nucleation and Slip Behavior Altered by Stochastic Normal Stress Heterogeneity
AU - Li, Meng
AU - Niemeijer, Andre
AU - van Dinther, Ylona
N1 - Publisher Copyright:
© 2024. The Author(s).
PY - 2025/1
Y1 - 2025/1
N2 - In recent laboratory experiments, varying nucleation locations of accelerating slip with changing nucleation lengths were observed. Spatial variations in effective normal stress, due to the controlling influence on fault strength and fracture energy, play an important role. We quantitatively explain how spatially heterogeneous effective normal stresses affect earthquake nucleation and slip behavior. We simulate a meter-scale laboratory experiment in a numerical earthquake sequence model with stochastically variable normal stresses. We identify five regimes of earthquake nucleation and slip behaviors, controlled by the ratio of the heterogeneity wavelength (Formula presented.) to the nucleation length (Formula presented.). When (Formula presented.), full ruptures are observed. Slip rates and recurrence intervals are similar to those on homogeneous faults with comparable averaged normal stress. When (Formula presented.), slow slip events and partial ruptures occur frequently and the nucleation length of each earthquake depends on the local stress level. We find locations of nucleation and arrest in both low and high normal stress regions (LSR and HSR, respectively) when (Formula presented.) and (Formula presented.) are of the same magnitude. When (Formula presented.), earthquakes nucleate in LSRs, and arrest in HSRs. However, HSRs and LSRs switch these roles when (Formula presented.). Interestingly, we observe that nucleation migrates from an LSR to its neighboring HSR in one earthquake, when (Formula presented.) is between the minimum and maximum local nucleation lengths. We observe a large amount of aseismic slip and associated stress drop in the initial LSR, which might be linked to the migration of foreshocks as documented in natural and laboratory observations. This improved understanding of earthquake nucleation is important in estimating the seismic potential of different fault patches for natural and induced seismicity.
AB - In recent laboratory experiments, varying nucleation locations of accelerating slip with changing nucleation lengths were observed. Spatial variations in effective normal stress, due to the controlling influence on fault strength and fracture energy, play an important role. We quantitatively explain how spatially heterogeneous effective normal stresses affect earthquake nucleation and slip behavior. We simulate a meter-scale laboratory experiment in a numerical earthquake sequence model with stochastically variable normal stresses. We identify five regimes of earthquake nucleation and slip behaviors, controlled by the ratio of the heterogeneity wavelength (Formula presented.) to the nucleation length (Formula presented.). When (Formula presented.), full ruptures are observed. Slip rates and recurrence intervals are similar to those on homogeneous faults with comparable averaged normal stress. When (Formula presented.), slow slip events and partial ruptures occur frequently and the nucleation length of each earthquake depends on the local stress level. We find locations of nucleation and arrest in both low and high normal stress regions (LSR and HSR, respectively) when (Formula presented.) and (Formula presented.) are of the same magnitude. When (Formula presented.), earthquakes nucleate in LSRs, and arrest in HSRs. However, HSRs and LSRs switch these roles when (Formula presented.). Interestingly, we observe that nucleation migrates from an LSR to its neighboring HSR in one earthquake, when (Formula presented.) is between the minimum and maximum local nucleation lengths. We observe a large amount of aseismic slip and associated stress drop in the initial LSR, which might be linked to the migration of foreshocks as documented in natural and laboratory observations. This improved understanding of earthquake nucleation is important in estimating the seismic potential of different fault patches for natural and induced seismicity.
UR - http://www.scopus.com/inward/record.url?scp=85213030445&partnerID=8YFLogxK
U2 - 10.1029/2024JB029857
DO - 10.1029/2024JB029857
M3 - Article
AN - SCOPUS:85213030445
SN - 2169-9313
VL - 130
JO - Journal of Geophysical Research: Solid Earth
JF - Journal of Geophysical Research: Solid Earth
IS - 1
M1 - e2024JB029857
ER -