4,445 research outputs found

    Shake Table Experiments on Multi-Story Aluminum Structures Using Scaled Ground Motions.

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    A shake table is a device used to simulate the seismic waves during an earthquake event and test the stability of the structure after an event. This table can be helpful in testing structural components or models. The primary objective of this study is to operate and verify the functionality of the shake table present at the Department of Civil Engineering’s structure research lab. The System Communication Software (SCSW), present at the University of Memphis’s Department of Civil Engineering lab, operates the shake table unidirectionally and requires ground motions to be uploaded to the software. Pacific Earthquake Engineering Research (PEER) provides strong ground motion data that was used to extract several ground motions for selection and scaling purposes for the study. As per ASCE 7-16, Chapter 16.2, non-linear response history analysis is applied to select and scale the motions. In addition to the ASCE provisions, the Spectral-Matching procedure in the frequency domain is practiced in scaling or matching of the ground motions for this study. The ground motions to be uploaded needs to be either load or displacement controlled. The extracted scaled ground motions as acceleration time histories are converted into displacement time histories and are uploaded to the SCSW software to control the shake table to displace. The scaled models are mounted on the shake table using bolted connections. Accelerometers are clamped on every story of the scaled model to measure the acceleration while being subjected to scaled ground motion. The data acquired from the accelerometers are raw, unprocessed, and thus need to be filtered for unwanted components or noise. The final processed and corrected accelerations are then compared with the output response at every story of all the scaled models from the 2D SAP2000 model for validation of the functionality of the shake table

    GPS source solution of the 2004 Parkfield earthquake

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    We compute a series of finite-source parameter inversions of the fault rupture of the 2004 Parkfield earthquake based on 1 Hz GPS records only. We confirm that some of the co-seismic slip at shallow depth (<5 km) constrained by InSAR data processing results from early post-seismic deformation. We also show 1) that if located very close to the rupture, a GPS receiver can saturate while it remains possible to estimate the ground velocity (~1.2 m/s) near the fault, 2) that GPS waveforms inversions constrain that the slip distribution at depth even when GPS monuments are not located directly above the ruptured areas and 3) the slip distribution at depth from our best models agree with that recovered from strong motion data. The 95th percentile of the slip amplitudes for rupture velocities ranging from 2 to 5 km/s is, 55 +/- 6 cm.Comment: 24 pages including supp. material

    Zero baseline correction of strong-motion accelerograms

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    A new method is proposed for standard baseline correction of strong-motion accelerograms. It is based on high-pass filtering of the uncorrected digitized accelerogram data. Unlike the parabolic baseline correction, the new method has well-defined frequency transfer function properties which are largely independent of the record length

    Nonstationary Stochastic Simulation of Strong Ground-Motion Time Histories : Application to the Japanese Database

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    For earthquake-resistant design, engineering seismologists employ time-history analysis for nonlinear simulations. The nonstationary stochastic method previously developed by Pousse et al. (2006) has been updated. This method has the advantage of being both simple, fast and taking into account the basic concepts of seismology (Brune's source, realistic time envelope function, nonstationarity and ground-motion variability). Time-domain simulations are derived from the signal spectrogram and depend on few ground-motion parameters: Arias intensity, significant relative duration and central frequency. These indicators are obtained from empirical attenuation equations that relate them to the magnitude of the event, the source-receiver distance, and the site conditions. We improve the nonstationary stochastic method by using new functional forms (new surface rock dataset, analysis of both intra-event and inter-event residuals, consideration of the scaling relations and VS30), by assessing the central frequency with S-transform and by better considering the stress drop variability.Comment: 10 pages; 15th World Conference on Earthquake Engineering, Lisbon : Portugal (2012

    Record Processing in ITACA, the New Italian Strong-Motion Database

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    The development of the new Italian strong-motion database ITACA (ITalian AC-celerometric Archive, http://itaca.mi.ingv.it) is in progress under the sponsorship of the National Department of Civil Protection (DPC) within Project S4, in the framework of DPC-INGV 2007–2009 research agreement. This work started from the alpha version of ITACA [8], where 2,182 3-component records from 1,004 earthquakes, mainly recorded by the National Accelerometric Network, RAN, operated by DPC, were processed and included in the database. Earthquake metadata, recording station information and reports on the available geologicalgeophysical information of 452 recording sites, corresponding to about 70% of the total, were also included. Subsequently, ITACA has been updated and will reach its final stage by the end of Project S4, around mid-2010, with additional features, improved information about recording stations, and updated records, including the Mw6.3 L’Aquila earthquake. All records were re-processed with respect to the alpha version [9], with a special care to preserve information about late-triggered events and to ensure compatibility of corrected records, i.e., velocity and displacement traces obtained by the first and second integral of the corrected acceleration should not be affected by unrealistic trends. After a short introduction of ITACA and its most relevant features and statistics, this paper mainly deals with the newly adopted processing scheme, with reference to the problems encountered and the solutions that have been devised

    Performance of Several Low‐Cost Accelerometers

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    Several groups are implementing low-cost host-operated systems of strong-motion accelerographs to support the somewhat divergent needs of seismologists and earthquake engineers. The Advanced National Seismic System Technical Implementation Committee (ANSS TIC, 2002), managed by the U.S. Geological Survey (USGS) in cooperation with other network operators, is exploring the efficacy of such systems if used in ANSS networks. To this end, ANSS convened a working group to explore available Class C strong-motion accelerometers (defined later), and to consider operational and quality control issues, and the means of annotating, storing, and using such data in ANSS networks. The working group members are largely coincident with our author list, and this report informs instrument-performance matters in the working group’s report to ANSS. Present examples of operational networks of such devices are the Community Seismic Network (CSN; csn.caltech.edu), operated by the California Institute of Technology, and Quake-Catcher Network (QCN; Cochran et al., 2009; qcn.stanford.edu; November 2013), jointly operated by Stanford University and the USGS. Several similar efforts are in development at other institutions. The overarching goals of such efforts are to add spatial density to existing Class-A and Class-B (see next paragraph) networks at low cost, and to include many additional people so they become invested in the issues of earthquakes, their measurement, and the damage they cause

    The engineering strong-motion database: A platform to access pan-European accelerometric data

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    This article describes the Engineering Strong-Motion Database (ESM), developed in the framework of the European project Network of European Research Infrastructures for Earthquake Risk Assessment and Mitigation (NERA, see Data and Resources). ESM is specifically designed to provide end users only with quality-checked, uniformly processed strong-motion data and relevant parameters and has done so since 1969 in the EuroMediterranean region. The database was designed for a large variety of stakeholders (expert seismologists, earthquake engineers, students, and professionals) with a user-friendly and straightforward web interface. Users can access earthquake and station information and download waveforms of events with magnitude 65 4:0 (unprocessed and processed acceleration, velocity, and displacement, and acceleration and displacement response spectra at 5% damping). Specific tools are also available to users to process strong-motion data and select ground-motion suites for codebased seismic structural analyses
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