SMIP 2002 Seminar

ShakeMap was designed primarily as a rapid response tool to portray the extent and variation of ground shaking throughout southern California immediately following significant earthquakes. The system now runs throughout California as well as in the Salt Lake City and Seattle areas, and it is being expanded to populated, seismically active regions nationally as resources permit. For rapid response, ShakeMap ground motion values are used for emergency response and loss estimation, assessment of damage to the lifeline and utility networks, and for providing information to the general public. However, ShakeMap can also be used as a pre-earthquake planning tool by generating ground motion estimates for a suite of potential earthquake scenarios. Estimates based on earthquake scenarios can provide a firm basis for loss estimation on a regional scale as well as provide utilities and other users a means of evaluating their emergency response capabilities. This paper will examine the practical applications of ShakeMap in emergency response, engineering, planning, training, and public education considering both current and future applications.

The ATC-54 Report, Guidelines for Using Strong-Motion Data for Postearthquake Response and Postearthquake Structural Evaluation, under preparation by the Applied Technology Council for the California Division of Mines and Geology, provides guidance on (1) the use of near-real-time computer-generated ground- motion maps in emergency response, and (2) the use and interpretation of strong-motion data to evaluate the earthquake response of buildings, bridges, and dams in the immediate postearthquake aftermath. Guidance is also provided on the collection of data describing the characteristics and performance of structures in which, or near which, strong-motion data have been recorded..

This paper describes portions of the document, Guidelines for Using Strong-Motion Data for Postearthquake Response and Postearthquake Structural Evaluation, currently being developed by the Applied Technology Council (ATC) for the California Division of Mines and Geology’s (CDMG) Strong Motion Instrumentation Program (SMIP) 2000 Data Interpretation Project. The focus of this paper is on the use of computer-generated ground- motion maps, i.e., TriNet ShakeMaps, for post-earthquake response applications. Two companion papers presented at the SMIP02 Seminar, both by C. Rojahn et al., focus, respectively, on the overall description of the Guidelines and on the use of strong-motion data for structural evaluation. The procedures outlined in this paper are a summary of the information contained in the current draft of the document, which addresses ShakeMap applications for ten areas of post-earthquake response. The general framework is given here, with illustration for one application – damaged buildings and safety inspections.

This paper describes portions of the document, Guidelines for Using Strong-Motion Data for Postearthquake Response and Postearthquake Structural Evaluation, currently being developed by the Applied Technology Council for the California Geological Survey (formerly, California Division of Mines and Geology) Strong Motion Instrumentation Program 2000 Data Interpretation Project. The focus of the paper is on guidance for using strong- motion data to evaluate the performance of structures in the immediate earthquake aftermath. Topics addressed include strong- motion data sources and processing, damage indicators that can often be observed in recorded data, and methods for rapid interpretation of strong-motion data to evaluate structural performance.

Various ground shaking and damage parameters are examined for post-earthquake applications. Peak ground motion values, elastic response spectra, spectrum intensity, drift spectrum, inelastic spectra, hysteretic energy spectrum, and two improved damage spectra are examined. The proposed damage spectra will be zero if the response remains elastic, and will be unity when the displacement capacity under monotonic deformation is reached. The damage spectra can be reduced to the special cases of normalized hysteretic energy and displacement ductility spectra. The proposed damage spectra are promising for seismic vulnerability studies and post-earthquake applications of existing facilities, and performance-based design of new structures.

This paper describes portions of the document, Guidelines for Using Strong-Motion Data for Postearthquake Response and Postearthquake Structural Evaluation, currently being developed by the Applied Technology Council (ATC) for the California Division of Mines and Geology’s (CDMG) Strong Motion Instrumentation Program (SMIP) 2000 Data Interpretation Project. The focus of this paper is on the use of computer-generated ground-motion maps, i.e., TriNet ShakeMaps, for emergency response applications. Two companion papers presented at the SMIP01 Seminar, by C. Rojahn et al. and by A.G. Brady and C. Rojahn, focus, respectively, on the overall description of the Guidelines and on the use of strong-motion data for structural evaluation. The procedures outlined in this paper are a summary of the information contained in the current draft of the document, which addresses ShakeMap applications for ten areas of emergency response. The general framework is given here, with illustration for one application – damaged buildings and safety inspections.

Ground and structure motions were recorded on 17 channels at Pacoima Dam during a magnitude 4.3 earthquake on January 13, 2001. These data are examined by system identification and finite element modeling to quantify the effects of nonuniform ground motion and the level of damping exhibited by the dam. The system identification study indicates the dynamic response of the dam is due mostly to two modes which have frequencies close to 5hz and damping in the range of 4% to 7% of critical. The displacement histories of the dam are reproduced fairly well by the finite element model, but differences in amplitudes for some of the channels remain to be resolved. In addition, more work is needed to obtain confidence in the results, especially the relatively high level of damping which seems to be present.

The Engineering Data Center (EDC) of the California Integrated Seismic Network (CISN) provides an Internet Quick Report (IQR) to distribute processed strong-motion data and detailed information on instrumented stations immediately after an earthquake. The coverage area of the IQR has been extended to statewide coverage and the Internet Data Report has been introduced. The EDC also has developed search functions to let users quickly access strongmotion data records from certain stations or certain structure types for different earthquakes based on station or structure characteristics.

Basin waves are polarized predominantly in the directions parallel to and normal to the edge of the basin, consistent with the assumption made by Joyner (2000). There are significant differences between the amplitudes of the horizontal component parallel to the basin edge, which is predominantly Love waves, and the horizontal component perpendicular to the basin edge, which is predominantly Rayleigh waves, although these amplitudes will be affected by the relative strength of the incoming waves, which depends on focal mechanism and other factors. This is also consistent with the assumption made by Joyner (2000). There is a significant dependence of the ground motion amplitude and duration on basin depth. Basin depth dependence was not included in the Joyner (2000) model. When depth increases away from the basin edge (i.e. when basin depth and basin edge distance are correlated), this can cause ground motion amplitudes and durations to increase away from the basin edge. The Husid plot derived from the velocity waveform provides an appropriate duration measure that is independent of the absolute amplitude level.

This paper summarizes the conclusions and recommendations of the COSMOS workshop on Strong-Motion Instrumentation of Buildings held in Emeryville, CA, on November 14 and 15, 2001. The recommendations are intended to provide guidance for implementation of the strongmotion element of the Advanced National Seismic System (ANSS) and for strong-motion instrumentation of buildings in general. The guiding objective of building instrumentation should be to gain understanding of the behavior of representative building types in order to improve general predictive models, by: 1) challenging, verifying or calibrating models; 2) calibrating design and retrofit rules (codes); and 3) calibrating post earthquake evaluation rules. National and regional priorities and building selection criteria are needed. The ANSS should take advantage of advances in instrumentation and monitoring technologies and should build partnerships with state and local agencies and private sector companies in order to extend the scope of instrumentation of buildings.

This paper is a summary of findings and recommendations of a Consortium of Organizations for Strong-Motion Operating Systems (COSMOS)/ Pacific Earthquake Engineering Center (PEER) Lifelines Program workshop on archiving and web dissemination of geotechnical data held on October 4 and 5, 2001. The concept that emerged from the workshop is a central hub that would function as a virtual data center through which data providers share as well as disseminate their data. Presentations during the first day showed that the development of a virtual center for web dissemination of linked geotechnical databases can be largely accomplished using existing technologies to link the organizational elements of the system. The primary needs are to: 1) define the functional requirements of a virtual center, 2) define data formats, data dictionaries, indexes, and exchange standards, and 3) define and link the organizational components of the overall system. The principal consensus recommendation for future development was that, initially, a pilot implementation of a virtual data center should be developed. The pilot system should involve several of largest data providers including California Department of Transportation (Caltrans), Pacific Gas and Electric Company (PG&E), California Geological Survey (CGS), and the U. S. Geological Survey (USGS). Building on this pilot system, the links could be expanded to include other data providers and the general user community.