By Ezra Jampole, Ph.D., P.E.
On 07 November 2016 (01:44:25 UTC) a M5.0 earthquake devastated the historic downtown of Cushing, Oklahoma. Within a week of the earthquake, EERI sent a reconnaissance team to Cushing to document the damage to the built environment and implement a business resilience survey in the historic downtown, shown in Figure 1. The team documented their observations and findings in a report, which addressed seismicity, geotechnical and ground motion effects, performance of buildings/lifelines, nonstructural components, emergency response, and social/economic impacts. Summarizing the observed building performance, unreinforced masonry (URM) buildings in the historic downtown (built circa 1900) sustained significant damage, including out-of-plumbness, partial collapses, and extensive façade damage. This pattern of damage to URM buildings has been observed following numerous earthquakes around the world. At the time of initial reconnaissance, 41 businesses in the historic downtown were surveyed: 59% of were open, 15% were closed, and 27% had either relocated, were seasonally closed, or had already closed prior to the earthquake. Damage to light frame homes and other non-URM structures was relatively minor, and there were minor disruptions to lifelines. Buildings in the business corridor, mostly constructed in the last thirty years, sustained little to no damage.
Figure 1. Cushing, Oklahoma (adapted from Google).
More than two years after the earthquake, I returned to Cushing’s historic downtown to observe how the community had rebuilt following the earthquake. One of the most common damage conditions observed by the EERI reconnaissance team following the earthquake was spalled brick from URM buildings, which effectively closed the streets in the historic downtown for several weeks after the earthquake. Figure 2 shows a building on N Cleveland Avenue that shed bricks onto the sidewalk (left), and the brick façade has since been replaced by metal sheeting (right).
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| (a) November 2016 | (b) December 2018 |
Figure 2. Brick façade repair.
Numerous damaged buildings have been demolished. The outer brick wythe of the Lion’s Club URM building, positioned at the end of a block of URM buildings on W. Broadway St., collapsed onto the street during the earthquake (Figure 3a). Additionally, the building had a permanent drift of at least 1% away from the adjacent building. In March 2017, the front of the building reportedly collapsed. The building has since been demolished, and metal siding panels now line the façade at the new end of the block (Figure 3b).
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| (a) November 2016, (adapted from EERI reconnaissance report) | (b) December 2018, from NW |
Figure 3. Lion’s Club Building demolished.
Several additional URM buildings with businesses along W. Broadway St. that sustained earthquake damage were demolished after the earthquake, as shown in Figure 4. An additional building was demolished along E Moses St. (Figure 5), however, there did not appear to be an operational business here prior to the earthquake.
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| (a) November 2016, from NE | (b) December 2018, from NW |
Figure 4. Buildings demolished in the historic downtown along W. Broadway St. at N. Cleveland Ave.
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| (a) July 2013 (Google) | (b) December 2018 |
Figure 5. Building on E Moses Street demolished after the earthquake.
Repairs have not been completed on numerous buildings. Figure 6a shows stone masonry that was dislodged during the earthquake, and two years after the earthquake is sitting on the fire escape below. Figure 6b shows a building that experienced an extensive out-of-plane exterior brick wall failure during the earthquake. Tarps now cover the openings in the façade, and bricks appear to have been gathered at the site, but reconstruction has not yet taken place. These buildings are representative of many damaged buildings in the historic downtown for which repairs have not been completed.
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| (a)December 2018, spalled masonry unrepaired | (b) December 2018, out-of-plane masonry wall failure unrepaired. |
Figure 6. Unrepaired damage conditions.
Figure 7 shows the Cimarron tower, the tallest building in Cushing, a concrete frame building with unreinforced clay brick and terra cotta infill masonry. At the time of EERI’s initial reconnaissance visit, the terra cotta cornice on the parapet at the roof level was being removed because of concerns that the masonry units were loose and posed a falling hazard. Two years after the earthquake, the ornamentation has not been replaced.
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| (a)November 2016, from SE | (b) December 2018, from SW |
Figure 7. Cimarron Tower cornice removed and not replaced.
The built environment in Cushing's historic downtown has not recovered, as evidenced by the numerous demolished and unrepaired buildings. However, it is clear that the town was already developing in areas away from the historic downtown prior to the 2016 earthquake, with most new commercial construction along the highway corridor. There appears to be less incentive to invest in rebuilding and reoccupying the older, damaged areas of town. Communities with older districts in disaster-prone areas may grapple with similar issues in the future, and should consider mitigating the risk to their vulnerable buildings.
