Introduced in this paper are several alternative ground-motion intensity measures ( IMs) that are intended for use in assessing the seismic performance of a structure at a site susceptible to near-source and/or ordinary ground motions. A comparison of such IMs is facilitated by defining the “efficiency” and “sufficiency” of an IM, both of which are criteria necessary for ensuring the accuracy of the structural performance assessment. The efficiency and sufficiency of each alternative IM, which are quantified via (i) nonlinear dynamic analyses of the structure under a suite of earthquake records and (ii) linear regression analysis, are demonstrated for the drift response of three different moderate- to long-period buildings subjected to suites of ordinary and of near-source earthquake records. One of the alternative IMs in particular is found to be relatively efficient and sufficient for the range of buildings considered and for both the near-source and ordinary ground motions.

A-1. Plot of probability of surface rupture relative to magnitude A-2. Plot of depth to top of surface rupture relative to magnitude for earthquakes in Next Generation Attenuation database B-1. Plot of multisegment fault as defined in 1996 and 2002 maps B-2. Plot of multisegment fault as defined in 2008 maps D-1. Diagram of a virtual dipping fault D-2. Plots showing effect of including hanging-wall term on median ground motion D-3. Plot showing the increase in Rjb for vertical faults F-1. Ground motions for two sites in the Central and Eastern United States without cluster model F-2. Ground motions for two sites in the Central and Eastern United States with cluster model G-1. Map of fault sources in the Intermountain West G-2. Slip-rate changes for Intermountain West faults H-1. Map of fault sources in the Pacific Northwest J-1. Plot showing increase in characteristic rate due to magnitude rounding J-2. Plot showing uncertainty in assigned slip rate for selected faults in Utah Appendix Tables: A-1. Depth to top of rupture E-1. Sampling interval details for non-California faults, truncated Gutenberg-Richter distribution G-1. Updated Intermountain West fault parameters G-2. Updated fault names for Intermountain West faults G-3. Intermountain West fault parameters by State H-1. Pacific Northwest fault parameters by State I-1. Rupture-model data for California Type-A faults I-2. List of significant changes to California Type-B faults I-3. Parameters for California Type-B faults I-4. Parameters for California Connected-B faults

One of the objectives in performance-based earthquake engineering is to quantify the seismic reliability of a structure at a site. For that purpose, probabilistic seismic demand analysis (PSDA) is used as a tool to estimate the mean annual frequency of exceeding a specified value of a structural demand parameter (e.g. interstorey drift). This paper compares and contrasts the use, in PSDA, of certain advanced scalar versus vector and conventional scalar ground motion intensity measures (IMs). One of the benefits of using a well-chosen IM is that more accurate evaluations of seismic performance are achieved without the need to perform detailed ground motion record selection for the nonlinear dynamic structural analyses involved in PSDA (e.g. record selection with respect to seismic parameters such as earthquake magnitude, source-to-site distance, and ground motion epsilon). For structural demands that are dominated by a first mode of vibration, using inelastic spectral displacement (S di ) can be advantageous relative to the conventionally used elastic spectral acceleration (S a ) and the vector IM consisting of S a and epsilon ( ). This paper demonstrates that this is true for ordinary and for near-source pulse-like earthquake records. The latter ground motions cannot be adequately characterized by either S a alone or the vector of S a and . For structural demands with significant higher-mode contributions (under either of the two types of ground motions), even S di (alone) is not sufficient, so an advanced scalar IM that additionally incorporates higher modes is used.KEY WORDS: probabilistic seismic hazard analysis (PSHA); probabilistic seismic demand analysis (PSDA); structural response (drift) hazard curves; ground motion record selection and scaling; ground motion intensity measure (IM); inelastic spectral displacement (S di )

Limitations of the existing earthquake ground motion database lead to scaling of records to obtain seismograms consistent with a ground motion target for structural design and evaluation. In the engineering seismology community, acceptable limits for 'legitimate' scaling vary from one (no scaling allowed) to 10 or more. The concerns expressed by detractors of scaling are mostly based on the knowledge of, for example, differences in ground motion characteristics for different earthquake magnitude-distance (M w -R close ) scenarios, and much less on their effects on structures. At the other end of the spectrum, proponents have demonstrated that scaling is not only legitimate but also useful for assessing structural response statistics for M w -R close scenarios. Their studies, however, have not investigated more recent purposes of scaling and have not always drawn conclusions for a wide spectrum of structural vibration periods and strengths. This article investigates whether scaling of records randomly selected from an M w -R close bin (or range) to a target fundamental-mode spectral acceleration (S a ) level introduces bias in the expected nonlinear structural drift response of both single-degree-of-freedom oscillators and one multi-degree-of-freedom building. The bias is quantified relative to unscaled records from the target M w -R close bin that are 'naturally' at the target S a level. We consider scaling of records from the target M w -R close bin and from other M w -R close bins. The results demonstrate that scaling can indeed introduce a bias that, for the most part, can be explained by differences between the elastic response spectra of the scaled versus unscaled records.(7) Regress (in log-log space) the resulting ratios of scaled over unscaled nonlinear structural responses on the corresponding scale factors. AMPLITUDE SCALING OF GROUND MOTION RECORDS 1825Depending on the vibration period (T ) and strength (R) of the SDOF structure, these results demonstrate that intra-bin scaling records up can result in nonlinear structural responses (here S I d ) that are biased high, whereas the converse is true for scaling down. The magnitude of the bias for a given scale factor is smaller for longer-period structures and for stronger (closer to elastic) structures; it also depends on the characteristics (e.g. M w and R close ) of the records that are scaled. These results are summarized further in the conclusions section. SDOF structures-inter-bin scalingAlternatively, one could either 'correct' for a scaling-induced bias by using results like those presented in this paper, or select records with spectra that are, once scaled, similar to that of the target S a , M w , and R close . Such a selection of the records to be scaled has been demonstrated to significantly reduce the potential for biased responses.