SPT-based probabilistic and deterministic assessment of seismic soil liquefaction potential

This paper presents new correlations for assessment of the likelihood of initiation (or “triggering”) of soil liquefaction. These new correlations eliminate several sources of bias intrinsic to previous, similar correlations, and provide greatly reduced overall uncertainty and variance. Key elements in the development of these new correlations are (1) accumulation of a significantly expanded database of field performance case histories; (2) use of improved knowledge and understanding of factors affecting interpretation of standard penetration test data; (3) incorporation of improved understanding of factors affecting site-specific earthquake ground motions (including directivity effects, site-specific response, etc.); (4) use of improved methods for assessment of in situ cyclic shear stress ratio; (5) screening of field data case histories on a quality/uncertainty basis; and (6) use of high-order probabilistic tools (Bayesian updating). The resulting relationships not only provide greatly reduced uncertainty, they also help to resolve a number of corollary issues that have long been difficult and controversial including: (1) magnitude-correlated duration weighting factors, (2) adjustments for fines content, and (3) corrections for overburden stress

Engineering Reconnaissance of the 24 August 2016 Central Italy Earthquake. Geotechnical Earthquake Engineering Reconnaissance GEER Association, Report No. GEER-050,

The central Italy earthquake occurred on 24 August 2016 at 03:36 AM local time. The magnitude is listed as M6.0 by INGV and M6.2 by USGS. Although initially reported as occurring at relatively shallow depths, the current source model from INGV places the hypocentral depth at 8 km, which is not especially shallow for shallow crustal earthquakes. The earthquake was located in a gap between two earlier damaging events, the 1997 M6.1 Umbria-Marche earthquake to the north-west and the 2009 M6.1 L’Aquila earthquake to the south-east. This gap had been recognized prior to the event as a zone of elevated risk (GdL Istituto Nazionale di Geofisica e Vulcanologia, hereafter INGV, 2016). The present event and those that preceded it occurred along the spine of the Apennine Mountain range on normal faults and had rake angles ranging from -80 to -100. Each of these events produced substantial damage to local towns and villages; the present event most strongly affected Arquata del Tronto, Accumoli, Amatrice, and Pescara del Tronto, with a loss of life as of this writing of 294, generally from collapses of unreinforced masonry dwellings. The NSF-funded Geotechnical Extreme Events Reconnaissance (GEER) association, with co-funding from the B. John Garrick Institute for the Risk Sciences at UCLA and the NSF I/UCRC Center for Unmanned Aircraft Systems (C-UAS) at BYU, mobilized a US-based team to the area from 5-9 September 2016. The US team worked in close collaboration with Italian researchers organized under the auspices of the Italian Geotechnical Society, the Italian Center for Seismic Microzonation and its Applications, the Consortium ReLUIS, Centre of Competence of Department of Civil Protection and the DIsaster RECovery Team of Politecnico di Torino. The objective of the Italy-US GEER team was to collect and document perishable data that is essential to advance knowledge of earthquake effects, which ultimately leads to improved procedures for characterization and mitigation of seismic risk. The Italy-US GEER team was multi-disciplinary, with expertise in geology, seismology, geomatics, geotechnical engineering, and structural engineering. Our approach was to combine traditional reconnaissance activities of on-ground recording and mapping of field conditions, with advanced imaging and damage detection routines enabled by state-of-the-art geomatics technology. This combination of reconnaissance techniques provides opportunities for innovative future study. The objective of this brief report is to provide to the technical community, emergency responders, and public an account of our activities and preliminary findings in a timely way. A more complete presentation of significant aspects of this event and our detailed findings will be presented in a subsequent Version 2 report

Engineering Reconnaissance following the October 2016 Central Italy Earthquakes. Version 2. Editors Paolo Zimmaro and Jonathan Stewart, Geotechnical Earthquake Engineering Reconnaissance GEER Association, Report No. GEER-050D

A team from the Geotechnical Extreme Events Reconnaissance (GEER) Association, supported by the National Science Foundation, has been mobilized to investigate geotechnical and geological aspects of the destructive earthquake sequence that occurred in Central Italy during a series of significant events October 26-30, 2016, which followed prior events August 24-29, 2016. GEER responded to the initial event sequence and reports resulting from that effort are published on the GEER web site. As before, GEER will operate in close collaboration with Italian engineers and scientists. GEER is also coordinating its reconnaissance activities to coincide with those of EERI, which will be led by Dr. Silvia Mazzoni. Giuseppe Lanzo, Professor at Sapienza University of Rome, and Jonathan P. Stewart, Professor and Chair of the Department of Civil and Environmental Engineering at UCLA, are the GEER team co-leaders. The US-based GEER team members participating in the investigation are Prof. Kevin Franke (Brigham Young University), Dr. Robert E. Kayen (US Geological Survey and UCLA), and Dr. Bret Lingwall (South Dakota School of Mines and Tech.). The GEER team is part of an international coordinated effort that involves cognizant Italian agencies (i.e. National Institute of Geophysics and Vulcanology, INGV; Rete dei Laboratori Universitari di Ingegneria Sismica, ReLuis; and European Centre for Training and Research in Earthquake Engineering, EUCENTRE Foundation and Italian Center for Seismic Microzonation and its Applications). Key Italian participants include: Prof. Luigi Di Sarno (ReLuis and University of Sannio), Profs. Sebastiano Foti and Filiberto Chiabrando (Politecnico di Torino), Dr. Fabrizio Galadini, Emanuela Falcucci, and Stefano Gori (INGV), Prof. Alessandro Pagliaroli (University of Chieti-Pescara), Dr. Giuseppe Scasserra and Prof. Filippo Santucci de Magistris (University of Molise), Prof. Francesco Silvestri (University of Napoli Federico II), Prof. Stefano Aversa (University of Napoli Parthenope) and MrDr. Paolo Tommasi (Consiglio Nazionale delle Ricerche, Rome). Also contributing to the GEER effort are researchers from New Zealand (Dr. Fernando Della Pasqua, GNS Science) and United Kingdom/Greece (team led by Prof. Anastasios Sextos, University of Bristol and Aristotle University of Thessaloniki). A full list of GEER team members will be compiled following deployment to the field. The GEER team assembled for this effort is multi-disciplinary, including geology, seismology, geotechnical engineering, structural engineering, and geomatics. Based on information gathered to date, field investigations for the GEER team and collaborators have focused on: (1) substantial surface fault rupture, apparently on the Mt. Vettore fault, (2) major rockfalls and landslides, including a large slide that dammed a river; and (3) building, bridge, and other infrastructure performance in villages and hamlets throughout the region, including many that had been well documented in reconnaissance following the 24-29 August event sequence. Earthquake engineering is an experience-driven field in which perishable data that can be used to advance our understanding should be systematically collected. The data collection will be performed using traditional mapping/observational methods and advanced imaging tools