 | |
| UTC time | 1916-10-18 22:04:00 |
|---|---|
| USGS-ANSS | ComCat |
| Local date | October 18, 1916 |
| Local time | 16:04 CST |
| Magnitude | 5.1 ML |
| Epicenter | 33°32′N 86°41′W / 33.53°N 86.69°W |
| Areas affected | Alabama, United States |
| Max. intensity | MMI VII (Very strong) |
| Casualties | None |
The 1916 Irondale earthquake struck in the north–central region of the U.S. state of Alabama on October 18. The strongest earthquake in state history, it registered an estimated Richter scale magnitude of 5.1 and resulted in minor damage. Damage was limited to Shelby and Jefferson counties and reached its maximum severity near the epicenter in the city of Irondale, including cracked windows, fallen chimneys, and dried-up wells. While there were no fatalities, the earthquake spawned widespread panic, prompting alarmed workers to evacuate tall buildings.
The earthquake originated in the Eastern Tennessee Seismic Zone, a fault noted for earthquakes of moderate magnitude. Faulting in the area is strike-slip-oriented, probably because of the Alabama-New York Lineament, which runs adjacent to the seismic zone. Several scientists believe that small earthquakes from the zone indicate the reactivation of deep, ancient faults. Alabama has seen roughly 20 earthquakes since the beginning of the 20th century. The earthquakes have been moderate, never reaching above magnitude 5.1, and they tend to cause damage only near their epicenters while reaching areas much further away. Major events include those in 1916, 1997, and 2003. Despite the lack of powerful seismic events in Alabama, earthquakes from nearby fault zones, including the New Madrid Seismic Zone, pose a serious threat to infrastructure. An earthquake similar in size to the 1916 Irondale event today could damage thousands of buildings and cause up to $1 billion in damage.[1]