Ground-Motion PreDiction

Predicting Seismic Ground-Motions in the Los Angeles Basin

 

Goal of Earthquake Early Warning (EEW) is the rapid estimation of shaking at a distant user site; if damaging shaking is expected, preparative actions can be triggered and executed before high-amplitude seismic waves arrive. Commonly, ground-motion parameters, such as instrumental intensity (MMI), are predicted from estimated magnitudes and distances using generic empirical ground-motion prediction equations (GMPEs). Finite fault geometry, directivity, and basin response effects are typically generalized or neglected, which can lead to a significant underestimation of shaking for large earthquakes (M>6.5). For enhanced ground-motion predictions considering 3D wave-propagation effects, we develop Support Vector Regression models from the SCEC CyberShake dataset (Graves et al., 2010); CyberShake encompasses full 3D wave-propagation simulations of >400k rupture scenarios (6.5≤Mw≤8.5) in Southern California as defined in UCERF 2.0. Our models predict the temporal evolution of MMI at a given user site (here: on rock and deep Los Angeles (LA) basin) using only information on the hypocenter location, magnitude, and rupture direction; they were determined from a subset (25%) of CyberShake simulations, but can explain MMI values of all >400k rupture scenarios with σ≈0.4. Our regression models also help to address EEW relevant questions, such as When do we need to issue an alert? or How much warning time can we expect? The models suggest that a moderate M6.5-7 earthquake along the Palos Verdes, Newport-Inglewood/Rose Canyon, Elsinore, or San Jacinto faults with a rupture propagating towards LA could cause very strong or severe shaking in the LA basin; warning times for these events could be >30 seconds.

 

References:

Graves, R., Jordan, T. H., Callaghan, S., Deelman, E., Field, E. H., Juve, G., Kesselman, C., Maechling, P., Mehta, G., Okaya, D., Small, P., Vahi, K., 2010: CyberShake: A Physics-Based Seismic Hazard Model for Southern California, Pure and Applied Geophysics, doi 10.1007/s00024-010-0161-6.

Last up-date:

12/13/2012

Maren Bӧse, Phd

Senior ReseaRch Fellow