MPC
Research Projects (2009-10)

Identifying Number

MPC-327

Project Title

Seismic Risk Assessment for the I-25/I-70 Corridor in the Mountain Plains Region of the U.S.

University

Colorado State University

Project Investigator

John van de Lindt

Description of Project Abstract

When one think of earthquakes the Mountain Plains Region does not come first to mind; rather, the West Coast, South America, Japan, and most recently Italy can easily be pictured. According to the U.S. Geological Survey (USGS) the largest earthquake on record for Colorado occurred in 1882:

"The earthquake of November 7, 1882, the first ever to cause damage at Denver, probably centered in the Front Range near Rocky Mountain National Park, and is the largest historical earthquake in the state. The magnitude is estimated to be about 6.2 on the Richter scale. In Boulder County the walls of the depot cracked, and plaster fell from walls at the university at Boulder. The quake was felt as far away as Salina, Kansas and Salt Lake City, Utah"

Seismic hazard assessment in Colorado has demonstrated that there is the potential for another event of this magnitude. Most structures in Colorado are designed with a focus on wind, which puts them at significant risk if an earthquake of M6 or greater were to occur. This type of situation has been termed low-occurrence high-consequence for natural hazards and is a challenge because of the public perception, i.e. a lack of need to consider this type of hazard.

According to the 2035 Regional Transportation Plan for the Intermountain Transportation Planning Region (2007) there is up to 38,000 vehicles on I-70 each day. Now, consider what would happen if this was disrupted for some period of time, and perhaps if I-25 which intersects I-70 was also disrupted because of one or more bridge or overpass failures. It is proposed in this problem statement to perform as risk assessment for the I-70 / I-25 intersection and surrounding area. This will include seismic risk assessment using FEMA's HAZUS software and quantification of the disruption including traffic flow based on estimates of downtime for overpasses and bridges in the region.

Project Objectives

The primary objective of this work is to quantify the expected loss for the I-25 / I-70 transportation system in the event of an earthquake. This will include de-conditioning the loss based on the occurrence probabilities of earthquakes of various magnitudes in this region.

Project Approach/Methods

The approach taken in this work can be separated into the following three tasks.

Task 1: HAZUS Analysis
Some existing analysis is available in Colorado through the Office of Emergency Management in Denver. These resources will be categorized and used to the extent possible. However, it will be necessary to run more detailed models using the HAZUS software for this particular area with the inclusion of bridges and overpasses in and around Denver. In this task a series of HAZUS models will be developed and run as appropriate to generate the necessary loss data for Task 2.

Task 2: Traffic Flow Model
In this task a traffic flow model will be applied to determine additional losses as a result of disruption and downtime for both I-70 and I-25. Basic economic rules with the assumptions clearly stated and vetted, to the extent possible, will be used to determine this additional loss. The traffic flow model will be deterministic in this case, but it is envisioned that the use of mean values here will not significantly affect the calculation of total loss. The sensitivity to this will be checked and, if needed, a probabilistic model will be applied.

Task 3: Seismic Risk Based on Loss
In the final task, the seismic risk will be shown based on expected loss, as well as scenario loss models for what might be deemed a 'typical" small, moderate, and large scenario in the region. These would correspond to earthquakes having a 50%, 10%, and 2% exceedance probability in 50 years, respetively.

MPC Critical Issues Addressed by Research

This work addresses MPC focus areas:

Focus Area #11: Traffic Operations and Management - Although the duration of an interruption in traffic flow as a result of a seismic event could be short to moderate, such a disruption could be devastating financially. In addition, because earthquakes in the region are rare, much of Colorado's transportation infrastructure is not designed to resist these types of loads.

Contributions/Potential Applications of Research

This transportation research study will provide information regarding the potential loss in the event of earthquakes of various magnitudes, as well as the expected value of the loss which accounts for the occurrence probability. This will enable regional officials to either further consider additional analyses and/or make decisions based on better understanding these low-occurrence high-consequence situations.

Technology Transfer Activities

The final report will be provided to the cognizant Colorado Department of Transportation and Colorado Emergency Management office in Denver for their use and discussion with the PI.

Time Duration

July 1, 2009 through June 30, 2010

Total Project Cost

$68,639.00

MPC Funds Requested

$31,224.00

TRB Keywords

Load rating; condition assessment; rural bridges.