1L10 - Supplemental USGS Work for NGA Project

Project Title/ID Number	Supplemental USGS Work for NGA Project—1L10
Start/End Dates	11/18/03 – 6/30/04
Project Leader	Paul Spudich (USGS/O)
Team Members	Jack Boatright (USGS/O), Rufus Catchings (USGS/O), Walter Mooney (USGS/O), Christopher Stephens (USGS/O), Shane Detweiler (USGS/O), Clare Steedman (USGS/O), Mark Goldman (USGS/O), Luke Blair (USGS/O), Linda Seekins (USGS/O), Fabio Perosi (USGS/O)

F=faculty; GS=graduate student; US=undergraduate student; PD=post-doc; I=industrial collaborator; O=other

Click on images to enlarge in a new window

1. Project Goals/Objectives:

Development of improved functional forms for directivity, based on isochrones theory that can be used by NGA attenuation relation developers in their new attenuation models.
Depths and uncertainties to 1.0 and 2.5 km/s S-wave velocities for all stations within the Bay Area and northern California that contribute strong motion recordings to the PEER/NGA database.
Processed accelerograms for 56 USGS 3-component records.

2. Role of this project in supporting PEER’s mission (vision):

This project contributes directly to the strong-motion data (C.) and meta-data (B.) in the PEER/NGA database, and to the development of physically appropriate attenuation relations (A.) for the regressions that form the heart of NGA.

3. Methodology Employed:

Task A will use isochrones theory to develop functional forms for directivity that have a basis in physics and can be easily used or generalized for nonplanar fault geometries. Computations will be done to check the applicability of isochrones theory to faulting scenarios appropriate for NGA project needs.
Task B will determine S-wave velocity structures for the 10 refraction lines in the Bay Area. These P and S-wave velocity structures obtained from refraction studies will be used to calibrate and revise the Brocher/Jachens/Wentworth Bay Area 3D velocity model. This revised model will be used to estimate the depth to the 1.0, 1.5, and 2.5 km/s S-wave velocities beneath the strong motion stations.
Task C will vet and process the 56 accelerograms using standard USGS processing procedures. Some additional effort will be required for the Superstition Hills data.

4. Brief Description of past year’s accomplishments (Year 6) & more detail on expected Year 7 accomplishments:

Achieved Milestones:

Presentation of preliminary results and solicitation of input at the December 2-3, 2003, Working Group 4 meeting.
Presentation of a suggested functional form, suitable for developer use, at the December 17-18, 2003 NGA workshop.

Achieved Milestones:

A database containing the P-wave and S-wave velocity structures for the 11 USGS refraction lines shot within the greater Bay Area since 1980, completed by mid-March 2004.
Processed USGS accelerograms delivered to the PEER/NGA database in January 2004.

5. Other Similar Work Being Conducted Within and Outside PEER and How This Project Differs:

The velocity model in the Bay Area lags greatly behind similar work being done in southern California.

6. Plans for Year 8 if project is expected to be continued:

None. Project will sunset this year.

7. Describe any actual instances where you are aware your results have been used in industry:

Results are too new.

8. Expected Milestones & Deliverables:

The main deliverable will be a report presenting and justifying the improved functional form for directivity. Remaining milestones are:

Presentation of a final report, in written form, documenting functional forms, including developer feedback, by the June 2004 workshop.

The critical deliverable for Task B is a table with the depths and uncertainties to the 1.0 and 2.5 km/s S-wave velocity for the stations in northern California that recorded earthquakes that are part of the PEER/NGA database. Remaining milestones are:

Calibration and revision of the Brocher/Jachens/Wentworth Bay Area 3D velocity model by April 2004.
A written report that documents the revision of the 3D model and compiles the depths and their uncertainties under the strong motion stations by June 2004.