All posts by Elizabeth Lundquist

Planning & Vision Meeting 2017

The planning and vision meeting is an opportunity for us to get ready for the 2017-2018 year. We will elect new officers, discuss dinner meeting topics, venues, short course, spring seminar and special topics. Pizza will be provided. Please RSVP.

Planning & Vision Meeting 2017

If you cannot attend but are interested in calling in to the meeting, please rsvp and indicate that you wish to call in. A meeting invite will be sent out later.

If you are interested in getting involved with the group please reach out to Ben Blanchette ( directly in advance of the meeting. There are positions we need to fill. I can answer any questions you might have.

 Thursday, June 29th

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Please consider joining us for another activity the week of May 22.  Several FHWA Geotechnical leaders will be in Seattle on Monday May 22, 2017 and will provide an overview of the FHWA Geotechnical program, technical assistance projects, and FHWA geotechnical research. Registration is now open (no cost) but please RSVP so we have a headcount.

FHWA Geotechnical Program

May 2017 Dinner Meeting

Please join us for our May dinner meeting next week on Thursday May 25th at the Best Western Executive Inn (Seattle). The Early Registration Deadline is this Friday, so please go and sign up and we hope to see you at this month’s dinner meeting.

The Evolving Role of Geomaterials in the Infrastructure Systems

We are excited to announce that Dr. J. David Frost, Professor at Georgia Tech will be speaking at our May dinner meeting at the Best Western Executive Inn (200 Taylor Ave N).

 Thursday, May 25th

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2017 Hennes Lecture at University of Washington

The GIGGS group at the University of would like to invite everyone to join them at their annual Hennes Lecture.  It is being held on Friday May 26th from 4pm-7pm on the UW campus. The presentation will be given my Jonathan Stewart, Chair of Civil Engineering at UCLA.

Friday, May 26
Presentation: 4:00 – 5:00
Reception: 5:00 – 7:00 (snacks provided, and drinks available for purchase)
The lecture is on the UW campus, in the Husky Union Building (HUB) Room 145
The event is free to attend and RSVP is not needed.
Contact: Shane Joseph Markus

Site response uncertainty and its implications for seismic risk characterization

Along with source and path effects, site response analysis is a vital component of earthquake ground motion characterization. Ground motion prediction equations (GMPEs) include terms for modeling site response that are based on simple metrics of site condition, such as the time-average shear wave velocity in the upper 30 m (VS30). Because site terms in GMPEs are derived from global databases, and are based on incomplete information on site conditions, their predictions represent average levels of site response conditional on VS30. Such predictions are referred to as ergodic.

Actual site response at a given site is likely to differ from this global average. Viewed in this context, the actual site response for a particular site and intensity measure is the sum in log units of the ergodic estimate from a global model and a (generally unknown) site term (denoted hS). If the level of site-specific error (hS) can be identified and used to adjust the ergodic model, the ground motion analysis is more accurate (i.e., bias is removed) and the dispersion of the predicted ground motions is reduced. Therefore, site-specific evaluations of site response are useful and will often reduce mean hazard levels at long return periods (due to dispersion reduction), although uncertainty in the site response is considered in an epistemic manner.

Important questions pertaining to this process include how should these evaluations be performed, how reliable are the resulting site response estimates, and how can the results be used in a probabilistically rigorous manner as required for hazard- or risk-based applications?

With this in mind, the presentation will cover:

  1. The physical processes responsible for site effects;
  2. The manner by which these processes are (or are not) reflected in relatively generic site factors used in GMPEs and in building codes;
  3. Effectiveness of site-specific geotechnical ground response analyses to estimate site effects;
  4. Recommended procedures for evaluating site-specific site response and its implementation in hazard/risk characterization for critical facilities.