A Multi-hazard World Means Buildings Must Multitask

5-18-15 Matthew Wall for LCH Blog

When we think of traditional Texas perils, high wind, hail, hurricanes and wildfires are top of mind. But, as Texas has gone from one earthquake “felt” in 100 years to more than 70 in the last ten, awareness is shifting to include seismic events too.

In fact, a recent USGS report identifies 17 areas within eight states with increased rates of induced seismicity.

That’s why we asked Dr. Michael Blanpied of the U.S. Geological Survey (USGS) to join us for our March 31 Texas State Collaborative (TSC) meeting in Austin where he very capably addressed the issue of “potentially induced seismicity”, and seismic activity in general.

Dr. Blanpied explained how USGS creates and updates seismic hazard maps every six years. This is essential information as seismic design ratings used for building codes are based on these maps. Through the 2008 hazard map update, earthquakes caused by industrial practices were removed from the analysis if certain conditions were met. This eliminated most earthquakes associated with mining, oil and gas production, and fluid injection. This was deemed to be the appropriate approach for designing long-term building codes, so now USGS is developing models to forecast the extent of hazardous ground shaking in the areas of recorded, significant, increased seismic activity.

A final hazard model is scheduled for release at the end of 2015.

We had a vivid reminder of the relevance of Dr. Blanpied’s presentation on May 7 when a 4.0 magnitude earthquake occurred 30 miles southwest of Dallas in Johnson County. In the aftermath of this earthquake, the Texas Railroad Commission required the operators of nearby disposal wells to perform testing regarding the effect of wastewater injection into subsurface rock formations. Thankfully, the earthquake caused no injuries, but it did cause minor damage to the foundation of two mobile homes.

And Texas isn’t the only state to experience increased seismicity. The Oklahoma Geologic Survey identified 5,415 earthquakes in 2014, and this tally omits many smaller earthquakes. The Central U.S. has seen a hundred-fold increase in earthquakes to the extent that Oklahoma now exceeds California in earthquake activity. Yes, you read that right.

This issue is driving complex scientific and social questions, especially as credible studies have now linked seismic activity to wastewater injection. However, our focus is not on causation, but whether or not the built environment is prepared regardless of causation.

Our TSC initiative is dedicated to helping Texas address shortcomings in the existing building code system, so do we now add earthquake to the mix? If so, where do we begin?

We are confronting a compounding natural hazard problem, but we cannot take our focus off the traditional perils either. The same evening of the 4.0 magnitude earthquake on May 7 in North Texas, at least two confirmed tornadoes touched down with severe weather continuing into the weekend.

This example represents a growing challenge facing disaster resilience advocates across the globe: what is the ideal mix of building science to address earthquake, high wind, and hail too?

The issue came up last year during our public awareness work with the Virginia Department of Emergency Management. Like Texas, Virginia has a coastline vulnerable to hurricanes, and residents have experienced deadly high-wind events, including tornadoes and the 2012 Derecho. In 2011, they experienced a 5.8 magnitude earthquake in Mineral that is considered the “most widely felt earthquake in U.S. history”. Even so, high wind is still the most common concern. That’s why we worked to identify a “two-for-one” building science solution to drive our messaging.

This video is the result of our effort and highlights what families can do to mitigate against both high wind and earthquakes. It is focused on one concept—a continuous load path, or a well-connected home where the roof ties to walls and walls tie to the foundation. The building principle is not new, but talking about it for high wind and seismic safety in the same conversation is atypical.

Texas and Virginia share a similar challenges regarding the need for integrated hazard mitigation solutions, and they are not alone. With or without induced seismicity, earthquakes can occur nearly anywhere. The same goes for high wind.

This uncertainty increases our resolve to find solutions that work for every location. We must build in a way that adequately addresses risks, even when they overlap. Delivering on multi-hazard mitigation solutions will challenge the disaster-resilience community, but we have the right team in place.

Let’s give families options that fit their reality even if it’s complicated.

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