Difference between revisions of "Moved:SCEC UGMS Committee Meeting"

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==Overview==
 
==Overview==
The SCEC Committee for UGMS met on May 12th from 10 a.m. to around 5:30 p.m at USC/SCEC in Los Angeles, CA. At the meeting, Tom Jordan (USC/SCEC) and his team presented details of the CyberShake platform, which completed long period ground-motion simulations for the Los Angeles region. They presented how model uncertainties have been addressed so far and showed results of probabilistic and deterministic calculations. At the end of these presentations the committee discussed the next steps toward the goal of preparing long period ground motion maps for the Los Angeles region, a task that will be performed in collaboration with the [http://collaborate.scec.org/gmsv SCEC GMSV TAG] committee chaired by Nico Luco (USGS).
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The [[UGMS|SCEC Committee for UGMS]] met on May 12th from 10 a.m. to around 5:30 p.m at USC/SCEC in Los Angeles, CA. At the meeting, Tom Jordan (USC/SCEC) and his team presented details of the CyberShake platform, which completed long period ground-motion simulations for the Los Angeles region. They presented how model uncertainties have been addressed so far and showed results of probabilistic and deterministic calculations. At the end of these presentations the committee discussed the next steps toward the goal of preparing long period ground motion maps for the Los Angeles region, a task that will be performed in collaboration with the [http://collaborate.scec.org/gmsv SCEC GMSV TAG] committee chaired by Nico Luco (USGS).
  
 
== Agenda ==
 
== Agenda ==

Revision as of 22:38, 9 February 2015

SCEC logo.png
SCEC Committee for Utilization of Ground Motion Simulations Meeting 2
Organizers: C.B. Crouse (URS) and Tom Jordan (SCEC/USC)
Date: Monday, May 12, 2014 (10:00-17:30)
Location: SCEC Boardroom, USC, Los Angeles, CA
Participants: 25 (by invitation only)

Overview

The SCEC Committee for UGMS met on May 12th from 10 a.m. to around 5:30 p.m at USC/SCEC in Los Angeles, CA. At the meeting, Tom Jordan (USC/SCEC) and his team presented details of the CyberShake platform, which completed long period ground-motion simulations for the Los Angeles region. They presented how model uncertainties have been addressed so far and showed results of probabilistic and deterministic calculations. At the end of these presentations the committee discussed the next steps toward the goal of preparing long period ground motion maps for the Los Angeles region, a task that will be performed in collaboration with the SCEC GMSV TAG committee chaired by Nico Luco (USGS).

Agenda

Presentation slides may be downloaded by clicking each title. PLEASE NOTE: Slides are the author's property. They may contain unpublished or preliminary information and should only be used while viewing the talk.

10:00 Welcome and introductions C.B. Crouse
10:10 SCEC UGMS Committee overview (pptx) C.B. Crouse
10:30 Overview of CyberShake and the SCEC ground motion simulation program (pdf) T. Jordan
11:30 Group Discussion All
12:00 Lunch
13:00 Development of the SCEC Community Velocity Models (pdf) T. Jordan
13:30 Comparisons among CyberShake models and with NGA models (pdf) T. Jordan
14:00 Group Discussion All
14:30 Break
15:00 Plans for future CyberShake development (pdf) T. Jordan
15:30 SCEC UGMS Committee Executive Session
17:30 Adjourn

Meeting Summary

Attendees

Member Attendees (in person)
C.B. Crouse - chair
Tom Jordan
Nico Luco
Bob Bachman
John Hooper
Jacobo Bielak
Charlie Kirchner
Marty Hudson
Marshall Lew
Member Attendees (remotely)
Ron Hamburger
Art Frankel
Norm Abrahamson
Rob Graves
Farzad Naeim
Curt Haselton
Members Absent
Paul Somerville
Jack Baker
John Anderson
Observers
Andreas Skarlatoudis
Fabio Silva
Kevin Milner
Brad Aagaard
Nenad Bijelic
Scott Callaghan
Greg Deierlein
En-Jui Lee
Ting Lin
Ricardo Taborda

New Members

Marshall Lew and Marty Hudson, geotechnical engineers in AMEC’s Los Angeles office, were added as new members and both attended the meeting.

Project Overview

Crouse presented an overview of the pilot project, with the ultimate objective of producing long period response spectral acceleration maps of the Los Angeles Metropolitan region. The plan is to develop the maps in coordination with (1) the SCEC Ground Motion Simulation Validation Technical Activity Group (GMSV-TAG), (2) other SCEC projects, such as Cybershake and UCERF, and (3) the USGS national seismic hazard project. The maps would be submitted to the NEHRP Provisions Update Committee next code cycle. The tentative schedule was attached to the minutes of the 1st UGMS committee meeting in April 2013.

Technical Presentations

Much of the meeting was devoted to a discussion of the CyberShake platform for generating ground-motion simulations throughout Southern California. T. Jordan first presented an overview of CyberShake and the SCEC ground motion simulation program. Jordan followed with presentations on the SCEC community velocity models, and comparisons of ground-motion predictions from CyberShake and the empirical NGA equations. Jordan also showed that Cybershake was able to reproduce long period ground motions from recent local earthquakes. Jordan’s final presentation was plans for future CyberShake development, which included extending the frequency band to 1.3 Hz to better define 1-sec period motions.

Discussion

Deterministic/stochastic methods were mentioned as possible approaches to expand CyberShake’s ability to model higher frequency ground motions. This was not viewed as a necessary development for the successful production of the long period maps, because the maps at higher frequencies would continue to be developed using the traditional empirical ground- motion prediction equations. Jordan asked the committee whether long period maps for the vertical component would be useful to structural engineers, since CyberShake automatically generates this component in addition to the two orthogonal horizontal components. There was general agreement that it would be informative to see vertical ground motions as a check with provisions for the vertical component that were added to the 2009 NEHRP Seismic Provisions.

Nico Luco said (and Jordan confirmed) that unlike the USGS seismic source model, the CyberShake so far has only computed ground motions from ruptures on known active faults, whereas, the USGS also includes random earthquakes in its seismic hazard analysis. The question to be addressed is whether the random earthquakes increase the ground motion hazard at long periods by an insignificant amount. The USGS can quickly answer this question by examining the source deaggregations in its PSHA.

Another discussion topic was the performance measures that should be used in validating the simulations from CyberShake. Simulated ground motions will be compared to ground motions from the empirical NGA equations, as a benchmark, but that exercise does not necessarily represent a validation. Art Frankel questioned whether the absolute values from CyberShake could be trusted because of the uncertainties in the fault slip function. Art is using 3-D simulations to compute long period basin amplification factors for the Puget Sound region. The uncertainty in the source slip function needs to be considered. Rob Graves was not present to offer his views on the subject, but the topic will need to be addressed in the future.

Resolutions

The UGMS continued to affirm that the long period mapping project will proceed on two parallel tracks, in which PSHA/DSHA will be conducted from the 3-D numerical simulations using CyberShake and from the traditional empirical approach using the NGA-West equations. It was agreed that the results from the 3-D simulations could be used to refine the equations ultimately used in the empirical approach. The topic of how to use the results from the two approaches to construct the long period maps was discussed will be deferred until the results are generated.

Sensitivity studies will be conducted to evaluate the effect of the near surface velocity structure on the long period ground motions. Varying the mesh size in the near surface would address the issue, and depending on the results, some refinements the the near surface velocity structure may be made.

Focus of Next Meeting

T. Jordan will present results of the 3-D Cybershake model at selected sites in Southern California. The results will consist of 5% damped, horizontal component response spectra, generated according to the requirements of Chapter 21 in the ASCE 7 standard. The approach will be the same as used by the USGS in creating the national risk-targeted Maximum Considered Earthquake (MCER) maps at 0.2-sec and 1.0-sec periods. The probabilistic and deterministic MCER response spectra would be computed for periods in the 2.0 to 10 sec range, and compared with similar results generated using the NGA West2 equations.

Action Item

Crouse will select sites for the CyberShake calculation of the MCER response spectra, and N. Luco will provide the Matlab routine to do calculate the probabilistic MCER from the hazard curves. Crouse will provide details on the calculation of the maximum direction shaking component.

Date for Next UGMS Committee Meeting

The next UGMS committee meeting is tentatively scheduled for one day in the fall of this year in the time window, November 3 to November 21. A Doodle poll will be sent to members to arrange a date.

Data of Interest

CyberShake Hazard Maps

Map of CyberShake sites. Purple sites are along a 10 km x 10 km mesh, orange sites are near SCSN broadband stations, and yellow sites are locations of interest.
Site Name NGA-1 3 second curve NGA-1 5 second curve NGA-2 3 second curve NGA-2 5 second curve
LADT LADT 3 sec LADT 5 sec LADT 3 sec LADT 5 sec
CCP CCP 3 sec CCP 5 sec CCP 3 sec CCP 5 sec
P22 P22 3 sec P22 5 sec P22 3 sec P22 5 sec
s429 s429 3 sec s429 5 sec s429 3 sec s429 5 sec
STG STG 3 sec STG 5 sec STG 3 sec STG 5 sec
s684 s684 3 sec s684 5 sec s684 3 sec s684 5 sec
s688 s688 3 sec s688 5 sec s688 3 sec s688 5 sec
PAS PAS 3 sec PAS 5 sec PAS 3 sec PAS 5 sec
s758 s758 3 sec s758 5 sec s758 3 sec s758 5 sec
SBSM SBSM 3 sec SBSM 5 sec SBSM 3 sec SBSM 5 sec
STNI STNI 3 sec STNI 5 sec STNI 3 sec STNI 5 sec
WNGC WNGC 3 sec WNGC 5 sec WNGC 3 sec WNGC 5 sec
s355 s355 3 sec s355 5 sec s355 3 sec s355 5 sec

Rupture Generator comparisons

Hypocenter distribution for source 244, rupture 5 (M6.55, Puente Hills)
Slips for a single realization of source 244, rupture 5 (M6.55, Puente Hills)
Hypocenter distribution for source 128, rupture 1296 (M8.15, Southern San Andreas)
Slips for a single realization of source 128, rupture 1296 (M8.15, Southern San Andreas)