SCEC Award Number 18179 View PDF
Proposal Category Individual Proposal (Data Gathering and Products)
Proposal Title Improved CVM upper mantle: A necessary step towards absolute crustal stress estimates in southern California
Investigator(s)
Name Organization
Eugene Humphreys University of Oregon A. Christian Stanciu University of Oregon
Other Participants
SCEC Priorities 1c, 3b, 3a SCEC Groups Seismology, SDOT, CXM
Report Due Date 03/15/2019 Date Report Submitted 03/15/2019
Project Abstract
 Our goals are to better understand the mantle density structure and improve constraints on the lithosphere kinematics in southern California. As a necessary step to achieve this goal we proposed to improve southern California upper mantle imaging through the use of modern tomography that includes better corrections for the near surface structure and anisotropy. We used an improved tomography algorithm that incorporates finite frequency kernels, 3-D ray tracing, ray weighting, and the SCEC CVM-S4 crustal model for the near surface corrections. Compared to other recent models, our new images resolve greater amplitudes for the upper mantle seismic structures, reduced thickness of the high-velocity structures, and more generally, modified structures.
Intellectual Merit Our tomography models contribute directly to the community velocity models for southern California and represent a base for better estimations of the absolute stress. More accurate tomography models allow for improved estimations of density variations that create tractions on the southern California crust. Our models incorporate better crustal corrections and 3-D ray tracing, improving our upper mantle imaging, our understanding of regional stress, and ultimately the hazard assessment.
Broader Impacts The project furthered the career of postdoc Christian Stanciu at University of Oregon. His work on mantle tomography in southern California allowed for further improvements on the algorithms used to image the upper mantle seismic structure. These improvements have applicability in other regions around the world, particularly in regions characterized by convergent tectonics.
Exemplary Figure Figure 1. P-wave velocity perturbations beneath southern California. Upper 440 km of model shown. Bottom: E-W cross sections through Transverse Range (A-A’) and Isabella (B-B’) anomalies (2018 SCEC Report, 18179, Improved CVM upper mantle: A necessary step towards absolute crustal stress estimates in southern California)