TY - JOUR

T1 - Modeling the Holocene slip history of the Wasatch fault (Utah)

T2 - Coseismic and postseismic Coulomb stress changes and implications for paleoseismicity and seismic hazard

AU - Bagge, Meike

AU - Hampel, Andrea

AU - Gold, Ryan

N1 - We are grateful to the editor, D.I. Schofield, the journal reviewers, M. Oskin and P. Jewell, as well as the U.S. Geological Survey internal reviewer, S. DeLong, for their constructive reviews, which improved the manuscript. We used the Generic Mapping Tools by Wessel and Smith (1998) to create some of the figures. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. government.

PY - 2019/1/1

Y1 - 2019/1/1

N2 - The Wasatch fault zone defines the eastern boundary of the actively extending Basin and Range Province (Utah, western United States) and poses a significant seismic hazard to the metropolitan areas along the Wasatch Range. A wealth of paleoseismological data documents ~24 surface-rupturing M w ≥ 7 earthquakes along the Wasatch fault during the past 6400 yr. Here, we simulated the Holocene earthquake sequence on the Wasatch, Oquirrh-Great Salt Lake, and West Valley faults using three-dimensional finite-element forward modeling with the goal to calculate coseismic and postseismic Coulomb stress changes and to evaluate the slip and magnitude of hypothetical present-day and future earthquakes. Our results show that a good fit between modeled and observed paleoevents and time-integrated slip rates can be achieved within the uncertainties of the paleoseismological record and model parameters like the fault geometry. The Coulomb stress change analysis for selected paleoearthquakes showed that maximum positive stress changes are induced on faults located along strike of the source fault, while faults parallel to the source fault are generally located in stress shadow zones. Postseismic viscoelastic relaxation considerably modifies the coseismic stress changes; the resulting transient stress changes are recognizable for more than 100 yr after an earthquake. The modeled present-day state of Coulomb stress changes shows that the Brigham City, Salt Lake City, and Provo segments of the Wasatch fault are prone to failure in a M w ≥ 6.8 earthquake. Our study shows that simulation of an entire earthquake sequence based on a paleoseismological record is feasible and facilitates identification of possible gaps and inconsistencies in the paleoseismological record. Therefore, forward modeling of earthquake sequences may ultimately contribute to improved seismic hazard estimates.

AB - The Wasatch fault zone defines the eastern boundary of the actively extending Basin and Range Province (Utah, western United States) and poses a significant seismic hazard to the metropolitan areas along the Wasatch Range. A wealth of paleoseismological data documents ~24 surface-rupturing M w ≥ 7 earthquakes along the Wasatch fault during the past 6400 yr. Here, we simulated the Holocene earthquake sequence on the Wasatch, Oquirrh-Great Salt Lake, and West Valley faults using three-dimensional finite-element forward modeling with the goal to calculate coseismic and postseismic Coulomb stress changes and to evaluate the slip and magnitude of hypothetical present-day and future earthquakes. Our results show that a good fit between modeled and observed paleoevents and time-integrated slip rates can be achieved within the uncertainties of the paleoseismological record and model parameters like the fault geometry. The Coulomb stress change analysis for selected paleoearthquakes showed that maximum positive stress changes are induced on faults located along strike of the source fault, while faults parallel to the source fault are generally located in stress shadow zones. Postseismic viscoelastic relaxation considerably modifies the coseismic stress changes; the resulting transient stress changes are recognizable for more than 100 yr after an earthquake. The modeled present-day state of Coulomb stress changes shows that the Brigham City, Salt Lake City, and Provo segments of the Wasatch fault are prone to failure in a M w ≥ 6.8 earthquake. Our study shows that simulation of an entire earthquake sequence based on a paleoseismological record is feasible and facilitates identification of possible gaps and inconsistencies in the paleoseismological record. Therefore, forward modeling of earthquake sequences may ultimately contribute to improved seismic hazard estimates.

UR - http://www.scopus.com/inward/record.url?scp=85059467487&partnerID=8YFLogxK

U2 - 10.1130/b31906.1

DO - 10.1130/b31906.1

M3 - Article

VL - 131

SP - 43

EP - 57

JO - Bulletin of the Geological Society of America

JF - Bulletin of the Geological Society of America

SN - 0016-7606

IS - 1-2

ER -