Preparing for Disaster


General Disaster Preparedness

Every year, geologic disasters around the globe cause millions of dollars of damage and take hundreds of lives. By reading more about specific hazards in your area (see additional Geological Survey of Alabama geological hazards pages in the main menu above) and by taking steps to educate yourself on response plans for you, your family, or your business, you can be better prepared for a disaster. For additional information on Alabama emergency preparedness not on this page, please visit the Alabama Emergency Management Agency website.


Recent Project: HAZUS Earthquake Damage and Loss Estimations

Project Description

The Geological Survey of Alabama (GSA) and Alabama Emergency Management Agency (AEMA) have worked together over several years planning for and studying earthquake hazards in the state. To support this planning, this year’s collaborative project (funded through the Federal Emergency Management Agency (FEMA) National Earthquake Hazard Reduction Program) includes modeling earthquake scenarios in the FEMA software HAZUS 4.2 to estimate damage and loss that could occur from potential earthquakes in three seismic zones impacting Alabama. Scenarios include 7.0 and 7.7 magnitude events for the New Madrid Seismic Zone, 5.5 and 6.0 magnitude events for the Fort Payne Area, 5.5 and 6.0 magnitude events for the Birmingham area, and 5.0 and 5.5 magnitude events for the Flomaton (Escambia County) area. The results of these scenarios were exported to HAZUS global summary reports and maps and can be downloaded by Clicking Here.

Data and Methods

The epicenter locations for the scenarios run for this project were based primarily on clusters of historical seismic activity in specific seismic zones. These seismic zones and their associated faults are ones for which earthquakes have had the greatest effect on Alabama and include the New Madrid Seismic Zone (NMSZ); Fort Payne and Birmingham areas in the Southern Appalachian Seismic Zone (SASZ), and the Flomaton area in the Bahamas Fracture Seismic Zone (BFSZ). Magnitudes were chosen based on historical earthquake magnitudes as well as geologic and structural characteristics of those areas. The scenarios were run as level 2 scenarios in HAZUS 4.2. While these level 2 scenarios included default engineering and census data, user-specified data maps for soils, liquefaction, landslides, and groundwater depth were also included. Soils, liquefaction, and landslides were based on data previously compiled at GSA. Groundwater depth data were extracted from U.S. Department of Agriculture Soil Survey Geographic Database (SSURGO). All map data were modified to match HAZUS software format requirements. For more information on HAZUS software, see FEMA’s webpage.

Seismic Setting

The three seismic zones having the greatest influence on Alabama are the New Madrid Seismic Zone, the Southern Appalachian Seismic Zone, and the Bahamas Fracture Seismic Zone (figure 1). Each of these zones has a history of seismic activity as recorded by seismic stations since the 1970s (U.S. Geological Survey (USGS), 2019) and historical newspapers recounting observed shaking effects of past events. The NMSZ has a history of moderate to large magnitude events, with the largest known occurring in the winter of 1811 and 1812 that included three earthquakes near 7.7 in magnitude (GSA, 2019a; USGS, 2009). Activity in the SASZ (a southern extension of the East Tennessee Seismic Zone) is the second most seismically active area of the eastern U.S. (second to the NMSZ; Powell and others, 1994). Although no large magnitude earthquakes are in historical records for the ETSZ, strong earthquakes (~6.0) have been extrapolated to occur about every 186 years according to Bollinger and others (1989), and the zone is considered capable of producing a large magnitude (>7.0) earthquake according to Wheeler and Frankel (2000). The largest known earthquake in Alabama associated with the SASZ occurred on October 1916 in northern Shelby County and is estimated to have been a VII on the Modified Mercalli Intensity scale (approximately 5.1 magnitude (Stover and Coffman, 1993)). The second strongest SASZ earthquake in Alabama occurred April 29, 2003, and was a 4.9 magnitude (4.4 MB, 4.6 MW, 4.9 LG) in DeKalb County, Alabama. Shaking from this earthquake was felt in multiple states, caused nonstructural damage, and triggered landslides and sinkholes in the area (GSA, 2019b; USGS, 2003, 2019). The Bahamas Fracture Seismic Zone also had a 4.9 magnitude earthquake in 1997 in Escambia County; and in the spring of 2019, a swarm of ten earthquakes occurred in the Flomaton area along the Pollard-Foshee Fault System, with the largest magnitude being a 3.1. Although a 1780 earthquake in the Pensacola area has been discussed in literature (Rucker, 1997), the records are questioned by some (Lane, 1983) to be more possibly related to an underwater landslide.

Strat Column

Figure 1. Earthquake epicenters in the southeastern U.S. Map data for the above map is from the U.S. Geological Survey (USGS) National Earthquake Information Center database.

Products

Products generated for this project include global summary reports and corresponding peak ground acceleration and peak ground velocity maps that can be used in earthquake planning and education outreach. Data generated in the global summary reports include damage and loss information for buildings, essential facilities, transportation and utility lifelines, economic loss, debris data, shelter requirements, casualties, shaking intensity, liquefaction potential, and landslide potential. To download the HAZUS global summary reports and maps associated with this project, Click Here to download the zipped file. This file includes data tables, information, and maps for:

References

Bollinger, G.A., Davison, Jr., F.C., Sibol, M. S., and Birch, J. B., 1989, Magnitude recurrence relations for the Southeastern United States and its subdivisions: Journal of Geophysical Research, v. 94, p. 2857-2873.

Geological Survey of Alabama, 2019a, The New Madrid Seismic Zone: Available Online Here.

Geological Survey of Alabama, 2019b, Earthquakes in Alabama, Earthquakes in Alabama: Available Online Here.

Lane, E., 1983, Earthquakes and seismic history of Florida: Florida Department of Natural Resources Information Circular 93, 8 p

Powell, C. A., Bollinger, G. A., Chapman, M. C., Sibol, M. S., Johnston, A. C., and Wheeler, R. L., 1994, A seismotectonic model for the 300 kilometer long eastern Tennessee seismic zone: Science, v. 264, p. 686-688.

Rucker, B. R., 1997, It can't happen here (?): A history of earthquakes in west Florida: Pensacola History Illustrated, v. 5, no. 2, p. 15-27.

Stover, C. W. and Coffman, J. L., 1993, Seismicity of the United States, 1568-1989 (Revised): Washington, D.C., United States Government Printing Office, U.S. Geological Survey Professional Paper 1527, 143 p.

U.S. Geological Survey, 2003, M4.6 Fort Payne, Alabama earthquake of 29 April 2003: Washington, D.C., United States Government Printing Office, poster.

U.S. Geological Survey, 2009, Earthquake hazard in the New Madrid Seismic Zone Remains a Concern: Washington, D.C., United States Government Printing Office, U.S. Geological Survey Fact Sheet 2009-3071, 2 p.

U.S. Geological Survey, 2019, Advanced National Seismic System Earthquake Catalog: Available Online Here.

Wheeler, R. L., Frankel, A., 2000, Geology in the 1996 USGS seismic-hazard maps, central and eastern United States: Seismological Research Letters, v. 71, no. 2, p. 273-282.