Wallace spells out seismic hazards

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Earthquakes > New Mexico building styles present a risk

By Arin McKenna

One of the highlights at Friday’s meeting of the Regional Coalition of LANL Communities was a presentation by Terry Wallace, principal associate director for global security at Los Alamos National Laboratory, on “The Seismic Hazard of New Mexico: Earthquakes & Building Codes.”

Wallace–who has a long list of credentials and awards–specializes in New Mexico seismology.

Wallace noted that scientists are able to study the area’s seismic history using the exposed geology in the canyons of the Pajarito Plateau, giving them a distinct advantage over other regions.

“It gives us a three-dimensional picture of what’s happening,” Wallace said. “It’s a snapshot in time.”
LANL’s presence has also made understanding the seismology of the area a priority.

“We understand the fault history of this particular area better than any other area of the United States,” Wallace said. “We’ve spent a tremendous amount of money in the last 50 years to study the geology of this region.”

The largest earthquake in New Mexico was just under magnitude 6 near Socorro in 1906.

The Pajarito fault system (PFS) is the greatest concern for Los Alamos. Over a 35 year period, 219 earthquakes have been recorded, with 89 of those between 1973 and 2007. However, the largest was a magnitude was 2.1, relatively small on the Richter scale. The Pajarito fault reaches to LANL’s west gate.

More worrisome is a small fault touching the current Chemistry and Metallurgy Research Replacement (CMRR) building, which was not recognized when the facility was built in 1952. This reinforces the need to build a new facility.

Wallace also raised concerns about other Northern New Mexico communities with comparison of New Mexico to Iran, where a 7.8 magnitude earthquake killed 15,000 people in 1978. Wallace believes a recent 7.8 earthquake in Iran will have a similar number of fatalities.

Construction practices in Iran are similar to that of many Northern New Mexico structures: unreinforced adobe with heavy roof structures.

“Right next to this is a number of Iranian facilities with modern construction from the last 20 years. And there is very little damage at all to those facilities,” Wallace said. “So in the end, building codes, building codes, building codes are the key to understanding hazards when we talk about this.”

To build safely in New Mexico, Wallace said scientists recommend building for a 7.3 earthquake. Any building other than a single family dwelling should be built to withstand .3g (gravity load) of force. A nuclear power plant must be designed to withstand 1g.