M7.6 in Costa Rica, Insured Losses Less Than $100M
05-Sep-12
A magnitude 7.6 earthquake occurred in northwestern Costa Rica on September 5, 2012. The earthquake was felt widely throughout Costa Rica for about 15 seconds. A preliminary tsunami warning from the Pacific Tsunami Warning Center was issued for the localized region of Nicaragua, Panama, and Costa Rica. Insured losses are expected to be minimal, mainly due to the earthquake's intermediate depth of 40 km.
Due to its low (18-degree) dip angle toward the northeast and its thrust type mechanism, today's earthquake appears to have occurred on the megathrust fault system of the Middle America Trench. The intermediate depth of 40 km suggests it occurred near the lower limit of stick-slip movement on the megathrust. Costa Rica has experienced earthquakes of similar magnitude in 1991 (M7.6), 1916 (M7.5), and 1950 (M7.7).
The USGS shakemap estimates a maximum ground shaking of Modified Mercalli Intensity (MMI) VI throughout the Nicoya Peninsula. This estimate conflicts slightly with the intensity map produced by "did you feel it" reports, which indicates intensity VIII as far as San Jose, 140 km from the epicenter.
Costa Rica Earthquake Intensity Map - September 5, 2012
Source: U.S. Geological Survey (USGS)
Costa Rica Earthquake USGS Shakemap - September 5, 2012
Source: U.S. Geological Survey (USGS)
For many earthquakes, these two types of maps estimate similar intensities, but human perceptions often differ from instrumental recordings and scientific calculations. In this case, the discrepancy could be attributable to any number of factors such as localized soil amplification or directionality, both of which would cause micro-variability in the duration and intensity of shaking.
If actual intensities were more similar to the PAGER estimate, insured losses will be little to none. If intensities were more similar to the Community Intensity map, then damage would be characterized by toppling contents with limited structural damage to vulnerable buildings, and insured losses would be expected not to exceed $100 million USD.
Users of EQECAT's WORLDCATenterprise are advised to consider event ID 4617 as the best proxy for this earthquake.
This event represents a M7.6 rupture of the Nicoya segment of the Middle America Subduction Zone, initiating mid-dip and rupturing simultaneously down-dip and up-dip toward the ocean floor. An alternate event ID suitable for sensitivity testing would be 2358, which represents a M7.6 Benioff earthquake (depth 40 to 60 km), located approximately 60 km northeast of today’s earthquake epicenter. Both of these events are in EQECAT's model region 105, Central America and Mexico Line Sources.
Engineering Risk and Site Evaluations
EQECAT Inc. and ABS Consulting are part of the ABS Group of Companies. ABS Consulting offers on-site risk assessments, evaluations and structural engineering services with more than 1,800 employees worldwide. ABS Consulting engineers and scientists use EQECAT catastrophe risk models to provide risk assessments, in addition to having performed inspections or repairs after more than 100 earthquakes and 25 major windstorms. Learn more about ABS Consulting's natural hazard risk assessment capabilities.
Subscribe to CatWatch email alerts, and receive CatWatch Catastrophe Reports to your inbox.