Wake County Hazard Mitigation Plan - January 2020

SECTION 4: RISK ASSESSMENT

The above map documents all earthquakes that have occurred within North Carolina; however, given the long distances across which earthquake impacts can be felt, these events do not encompass all earthquakes that have affected North Carolina. The following data, detailed in Table 4.23, was compiled and presented in the 2015 Wake County Hazard Mitigation Plan and remains relevant to the planning area. Table 4.23 – Historical Earthquakes Impacting North Carolina

Richter Scale (Magnitude)

MMI (Intensity)

MMI in North Carolina

Date

Location

12/16/1811 – 1 12/16/1811 – 2 12/18/1811 – 3 01/23/1812 02/071812 04/29/1852 08/31/1861 12/23/1875 08/31/1886 05/31/1897 01/01/1913 02/21/1916 07/08/1926 11/03/1928 05/13/1957 07/02/1957 11/24/1957 10/27/1959 * 07/13/1971

NE Arkansas NE Arkansas NE Arkansas

8.5 8.0 8.0 8.4 8.7 5.0 5.1 5.0 7.3 5.8 4.8 5.5 5.2 4.5 4.1 3.7 4.0 4.0 3.8 4.6 4.1 3.5

XI

VI VI VI VI VI VI

X X

New Madrid, MO New Madrid, MO Wytheville, VA Wilkesboro, NC Central Virginia Charleston, SC Giles County, VA Union County, SC

XI

XII

VI

VII VII

VII

VI

X

VII

VIII

VI VI

VII VII VII

Asheville, NC

VII VII

Mitchell County, NC

Newport, TN

VI VI VI VI VI VI VI VI VI

VI VI VI VI VI VI VI VI VI

McDowell County, NC Buncombe County, NC Jackson County, NC

Chesterfield, SC

Newry, SC Alcoa, TN

11/30/1973 11/13/1976 05/05/1981

Southwest Virginia

Henderson County, NC

* Conflicting reports on this event, intensity in North Carolina could have been either V or VI Source: 2015 Wake County Hazard Mitigation Plan (This information compiled by Dr. Kenneth B. Taylor and provided by Tiawana Ramsey of NCEM. Information was compiled from the National Earthquake Center, Earthquakes of the US by Carl von Hake (1983), and a compilation of newspaper reports in the Eastern Tennessee Seismic Zone compiled by Arch Johnston, CERI, Memphis State University (1983)). Probability of Future Occurrence Ground motion is the movement of the earth’s surface due to earthquakes or explosions. It is produced by waves generated by a sudden slip on a fault or sudden pressure at the explosive source and travels through the earth and along its surface. Ground motion is amplified when surface waves of unconsolidated materials bounce off of or are refracted by adjacent solid bedrock. The probability of ground motion is depicted in USGS earthquake hazard maps by showing, by contour values, the earthquake ground motions (of a particular frequency) that have a common given probability of being exceeded in 50 years. Figure 4.8 reflects the seismic hazard for Wake County based on the national USGS map of peak acceleration with two percent probability of exceedance in 50 years. To produce these estimates, the ground motions being considered at a given location are those from all future possible earthquake magnitudes at all possible distances from that location. The ground motion coming from a particular magnitude and distance is assigned an annual probability equal to the annual probability of occurrence of the causative magnitude and distance. The method assumes a reasonable future catalog of earthquakes,

Wake County Multi-Jurisdictional Hazard Mitigation Plan 2019

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