LELAND STANFORD JUNIOR UNIVERSITY, THE
Understanding seismic ground motion in the high frequency range (>1 Hz) is of substantial interest to the engineering community since the resonance frequency of most man-made structures lies within it. In this frequency range, ground motion is relatively incoherent and all frequencies are present, suggesting a source process that excites waves of all wavelengths. This project explores earthquake rupture propagation on rough faults with the working hypothesis that the irregular propagation induced by roughness might be responsible for producing observed levels of high frequency radiation. In particular, natural faults are well described as self-similar fractal surfaces: roughness is present at all scales and the amplitude of the roughness associated with a particular wavelength is proportional to that wavelength. Slip on nonplanar faults perturbs the local stress field, causing local accelerations and decelerations of propagating ruptures and the emission of seismic waves. In addition to the specific focus on high frequency ground motion, the project investigates general characteristics of earthquake dynamics on nonplanar faults.
These research questions will be addressed using direct numerical simulations of dynamic ruptures on nonplanar faults. The faults are governed by rate-and-state friction laws featuring extreme velocity-weakening behavior at coseismic slip rates, as observed in laboratory experiments. The off-fault response is modeled as that of a Drucker-Prager elastic-plastic material (similar to a Mohr-Coloumb material) in either a rate-independent or viscoplastic formulation.
The irregular geometries are handled using a coordinate mapping technique and high order finite differences are used to approximate the governing equations numerically. The particular numerical method features several mechanisms (upwinding and the adaptive selection of finite difference stencils) that prevent the development of spurious oscillations that would otherwise contaminate the solution at the high frequencies of interest.
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| AWARD OVERVIEW |
| Award Number |
0910574 |
Funding Agency |
National Science Foundation |
| Total Award Amount |
$250,326 |
Project Location - City |
Stanford |
| Award Date |
08/31/2009 |
Project Location - State |
CA |
| Project Status |
Completed |
Project Location - Zip |
94305-4124
|
| Jobs Reported |
0.00 |
Congressional District |
14 |
| Project Location - Country |
US |
|
|
Recipient Information
(Grants)
| Recipient Information (Grants) |
|
Recipient Name
|
LELAND STANFORD JUNIOR UNIVERSITY, THE |
| Recipient DUNS Number |
009214214
|
| Recipient Address |
450 SERRA MALL |
| Recipient City |
STANFORD |
| Recipient State |
California |
| Recipient Zip |
94305-2004 |
| Recipient Congressional District |
14 |
| Recipient Country |
USA |
Required to Report Top 5
Highly Compensated Officials |
No |
Projects and Jobs Information
| Projects and Jobs Information |
| Project Title |
Collaborative Research: Earthquakes on Nonplanar Faults: Rupture Dynamics and High Frequency Ground Motion |
| Project Status |
Completed |
| Final Project Report Submitted |
Yes |
| Project Activities Description |
Research & Public Policy Analysis |
| Quarterly Activities/Project Description |
This award is supporting one postdoctoral researcher and provides one summer month of salary for the PI per year. We have completed development of the finite difference code described in the Award Description. Rigorous proofs of stability and accuracy were obtained in collaboration with Jan Nordstrom from Uppsala University in Sweden. We have published one paper describing our numerical methods to the Journal of Scientific Computing and another is in press at the same journal. We have also applied the code to study rupture dynamics with strongly rate-weakening friction laws and off-fault plasticity. This was done for both flat faults and rough faults, and we have now published two papers in the Bulletin of the Seismological Society of America on the subject (in the October 2011 issue). We are now investigating how fault roughness increases the resistance to slip and are preparing a paper on this topic; that will be completed this summer We are also attempting to establish a quantitative link between the spectra of high frequency ground motion records and the statistical properties of fault roughness. We are looking at how the radiation pattern, including directivity effects, varies as a function of frequency. Finally, we have generated an ensemble of rupture models on nonplanar faults to examine statistical properties of ruptures. We have found that at the stress levels at which natural faults are expected to operate, most ruptures that nucleate are immediately arrested. Only a few become large events, which is consistent with known earthquake statistics. The postdoc is preparing a paper on this. No additional expenses will be posted to this award.
|
| Jobs Created |
0.00 |
| Description of Jobs Created |
None at this time |
Purchaser Information
(Grants)
| Purchaser Information |
| Contracting Office ID |
Not Reported |
| Contracting Office Name |
Not Available |
| Contracting Office Region |
Not Available |
| TAS Major Program |
49-0101 |
| Award Information |
| Award Date |
08/31/2009 |
| Award Number |
0910574 |
| Order Number |
|
| Award Type |
Grants |
| Funding Agency ID |
49 |
| Funding Agency Name |
National Science Foundation |
| Funding Office Name |
Not Available |
| Awarding Agency ID |
49 |
| Awarding Agency Name |
National Science Foundation |
| Amount of Award |
$250,326 |
| Funds Invoiced/Received |
$250,326 |
| Expenditure Amount |
$250,326 |
| Infrastructure Expenditure Amount |
$0 |
| Infrastructure Purpose and Rationale |
Not Reported |
| Infrastructure Point of Contact Name |
Not Reported |
| Infrastructure Point of Contact Email |
Not Reported |
| Infrastructure Point of Contact Phone |
Not Reported |
| Infrastructure Point of Contact Address |
Not Reported |
| Infrastructure Point of Contact City |
Not Reported |
| Infrastructure Point of Contact State |
Not Reported |
| Infrastructure Point of Contact Zip |
Not Reported |
Product or Service Information
(Grants)
| Product or Service Information |
| Primary Activity Code |
**K |
| Activity Description |
Research & Public Policy Analysis |
| Sub-Awards Information |
| Sub-awards to Organizations |
0 |
| Sub-award Amounts to Organizations |
$0 |
| Sub-Awards to Individuals |
0 |
| Sub-Award Amounts to Individuals |
$0 |
| Number of Sub-awards less than $25,000/award |
0 |
| Amount of Sub-awards less than $25,000/award |
$0 |
| Number of payments to vendors greater than $25,000 |
0 |
| Total Amount of payments to vendors greater than $25,000/award |
$0 |
| Number of payments to vendors less than $25,000/award |
33 |
| Total Amount of payments to vendors less than $25,000/award |
$10,873 |
| Location Information |
| Latitude, Longitude |
37º 25' 35",
-122º 10' 27" |
| Congressional District |
14 |
| Address 1 |
Stanford University |
| Address 2 |
340 Panama Street |
| City |
Stanford |
| County |
Santa Clara |
| State |
CA |
| Zip |
94305-4124 |
|
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