Recent cee_ucla_earthquake items

Implications of California vertical array data for the analysis of site response with 1D geotechnical modeling

Fri, 31 Aug 2018 00:00:00 +0000

Executive Summary Along with source and path effects, site response is an essential component of ground motion prediction. Widely used ground motion models (GMMs), also known as ground motion prediction equations, provide an ergodic representation of each component in the sense that observations from global databases during the observation period (generally the last few decades) are taken to apply for a particular site and tectonic setting of interest, following conditioning on relevant parameters (magnitude, distance, time-averaged shear wave velocity in the upper 30 m, VS30). Such models inherently average across effects that may exhibit location-to-location variability, increasing model dispersion. The use of non-ergodic site response has gained increasing attention in recent years as a means by which to increase model accuracy and reduce model dispersion, both of which affect the outcomes of seismic hazard analysis. The analysis of non-ergodic site response can, in general,...

ENGINEERING RECONNAISSANCE FOLLOWING THE AUGUST 24, 2016M6.0 CENTRAL ITALY EARTHQUAKE

Tue, 14 Feb 2017 00:00:00 +0000

ENGINEERING RECONNAISSANCE FOLLOWING THE AUGUST 24, 2016M6.0 CENTRAL ITALY EARTHQUAKE

NGA-Subduction site database

Wed, 8 Feb 2017 00:00:00 +0000

NGA-Subduction site database

Development of NGA-Subduction database

Wed, 8 Feb 2017 00:00:00 +0000

Development of NGA-Subduction database

Implications of California Vertical Array Data for Modeling of Non-Ergodic Site Response

Fri, 7 Oct 2016 00:00:00 +0000

Implications of California Vertical Array Data for Modeling of Non-Ergodic Site Response

Probabilistic Seismic Hazard Analysis for a Dam Site in Calabria (Southern Italy)

Mon, 19 Oct 2015 00:00:00 +0000

Probabilistic seismic hazard analysis (PSHA) are performed for routine applications using source models and ground motion prediction equations (GMPEs) recommended by a government agency (e.g., US Geological Survey) or an expert panel (e.g., SHARE project). For important projects, site-specific PSHA involves critical analysis of GMPEs and sources for the application region. We adopt the latter approach for a dam site in Calabria (southern Italy), a high seismic hazard region. Following SHARE convention, we consider faults sources, background zones, and area sources. We identify several problems with assigned maximum magnitudes in the SHARE model for fault and in-slab subduction sources. We add two sources not present in some prior inventories – the crustal Lakes fault and the Calabrian arc subduction interface. Following procedures developed for the Global Earthquake Model, we select GMPEs that are much better constrained in the hazard-controlling range of magnitudes and distances...

Applicability of levee fragility functions developed from Japanese data to California’s Central Valley

Wed, 6 Aug 2014 00:00:00 +0000

A fragility model for seismic deformations of levees was developed in a separate study using case history data from the Shinano River region of Japan (SRJ). In that model, levee fragility was shown to be principally related to ground motion intensity, geomorphology, and ground water level relative to the levee base. Our objective in this manuscript is to demonstrate the applicability of the developed fragility models for geotechnical conditions along urban levees in the Central Valley region of California (CVC). For this purpose, we compare SPT penetration resistance data (in the form of energy- and overburden-corrected blow counts) between regions for common soil types conditional on geology and topography. Among the geologic categories considered, arguably the most important is Holocene flood plain deposits, which comprise 38% of investigated sites in CVC and 97% in the SRJ. Within this geological unit, we find penetration resistance data for coarse-grained soils in the SRJ...

Incorporating Soil-Structure Interaction intoSeismic Response Analyses for Buildings

Fri, 25 Jul 2014 00:00:00 +0000

Soil-structure interaction (SSI) analysis evaluates the collective response anddynamic interplay of three linked systems: the structure, the foundation, and the soil underlying and surrounding the foundation. Problems associated with practical application of SSI for building structures are rooted in a poor understanding of fundamental SSI principles. Implementation in practice is hindered by a literature that is difficult to understand, and codes and standards that contain limited guidance and, in some cases, are proprietary. A recent report published by the National Institute of Standards and Technology (NIST) provides a mechanism for advancing the state of practice in SSI for practicing engineers. It offers a synthesis of the body of SSI literature, distilled into a concise narrative and harmonized under a consistent set ofvariables and units. Techniques are described by which SSI phenomena such as foundation-soil compliance and damping (inertial interaction), and foundation-to-free-field...

Measurements of dynamic impedance for a model levee on peat

Thu, 11 Apr 2013 00:00:00 +0000

An eccentric mass shaker mounted to the crest of a model levee resting on very soft peat soil was used to measure dynamic base shear-displacement and base moment-rotation relations. The model levee rotated and translated visibly during testing, exhibiting a response that deviates significantly from the one-dimensional wave propagation assumption often used to analyze the seismic response of levees. We evaluate complex-valued stiffness and damping of the levee-foundation soil interaction for translational and rotational modes of vibration. The damping is strongly dependent on frequency, indicating that it is controlled by radiation of energy away from the vibrating levee. These radiation damping effects are dominant even at low frequencies that are well within the range of engineering interest for ground failure evaluations. Interestingly, the levels of radiation damping are roughly comparable, when expressed as percentage of critical, to predictions from classical models for...

Remote monitoring of a model levee constructed on soft peaty organic soil

Wed, 10 Apr 2013 00:00:00 +0000

Remote data monitoring was performed to measure settlement and pore pressure in soft peat beneath a model levee constructed in the Sacramento / San Joaquin Delta. Consolidation and secondary compression behavior was monitored following construction and dynamic testing of the model levee using piezometers embedded in the peat and an in-place horizontal inclinometer at the base of the model levee. A solar powered data acquisition system was used to gather the data, and a modem transmitted the data to a web-based interface. This system enabled us to (i) know when primary consolidation had finished prior to testing, (ii) observe the large influence of secondary compression on observed settlements, and (iii) observe a lack of any significant post-cyclic settlement. The initial change in pore pressure was predicted well using Skempton's pore pressure parameters.

Comparison of ground motion attributes from 2011 Tohoku-oki mainshock and two subsequent events

Wed, 10 Apr 2013 00:00:00 +0000

The M_w 9.0 Tohoku-oki Japan earthquake and many of its subsequent aftershocks and triggered events were very well recorded, providing opportunity for detailed study of source, path, and site effects. In previous work, we utilized mainshock data to demonstrate faster attenuation with distance in backarc than in forearc regions, positive event terms for high frequency intensity measures for multiple ground motion prediction models, and minimal scaling of site amplification with V_s30 at high frequencies. In this paper, we consider two subsequent events, one M_w 6.7 on the plate interface that ruptured in the mainshock and one M_w 6.3 inland from the volcanic front, to examine if similar ground motion features are apparent from these data sets. We continue to find evidence for the divergence in attenuation rate in forearc and backarc regions, despite the fact that the events are located on opposite sides of the volcanic front. The site...

Groundwater level evaluation for river flood control levees and its effect on seismic performance