Dynamic Rupture Scenarios of Large Earthquakes on the Hayward Calaveras Rodgers Creek Fault System, California Using Observations from Geology and Geodesy

Session: Exploring Rupture Dynamics and Seismic Wave Propagation Along Complex Fault Systems
Type: Oral
Date: 4/29/2020
Time: 02:45 PM
Room: 110 + 140
Description: 

The Hayward-Calaveras-Rodgers Creek fault system in California is a major contributor to the 72% probability of the San Francisco Bay Area producing a magnitude 6.7 or larger earthquake by the year 2043 [Field et al., 2015]. Given that this fault system runs through a densely populated area, a large earthquake in this region is likely to dramatically affect the lives of millions of people. This study produces scenarios of large earthquakes on this fault system, using the tool of spontaneous (dynamic) rupture simulations. These types of physics-based computational simulations require information about the 3D fault geometry, the physical rock properties including fault friction and the initial stress conditions [e.g., Harris, 2004]. In terms of fault geometry, the multi-fault system includes the Hayward fault, which is connected at its southern end to the Central and Northern Calaveras faults and at its northern end to the Rodgers Creek fault. Both the Hayward fault and the Rodgers Creek fault have a record of large earthquakes [e.g., Lienkaemper et al., 2010; Hecker et al., 2005]. Geodetic investigations of the fault system’s slip-rate pattern provide images of where the fault surfaces at depth are creeping or locked, and this information helps us choose appropriate initial stress conditions for our simulations. A 3D geologic model of the Hayward fault system provides the 3D rock units and fault structure at depth [Graymer et al., 2005], while field samples from rocks collected at Earth’s surface provide friction parameters [Morrow et al., 2010]. We use all of this knowledge to discover how large earthquakes nucleating on this partially creeping fault system operate. We find that large earthquakes starting on the Hayward fault or on the Rodgers Creek fault may be slowed or stopped in their progress, depending on how much energy is stored in the creeping regions of the Hayward and Central Calaveras faults. It appears that large earthquakes starting on either of these two faults might not rupture the Northern Calaveras fault.

Presenting Author: Ruth Harris

Authors