Pocahontas, AR Earthquake, 21-October-1999

If you live in the vicinity of this earthquake we urge you to fill out a felt report. Even if you did not feel the earthquake, you can help us determine the extent of the felt area by letting us know where it was not felt. Your response will help CERI scientists better understand the effects of seismic activity in the New Madrid area.

Preliminary Source Parameters

• Date: 99/10/21
  
• Time(CDT): 03:18
  
• Latitude: 36°30'N (36.5113 DD)
  
• Longitude: 91°4'W (-91.0497 DD)
  
• Depth: 19.29 km
  
• Magnitude (MbLg) = 3.9
  

Click here for a seismogram.

Click here for an intensity map of this earthquake.

A small earthquake (likely an aftershock) occurred October 21, 1999 at about 3:49AM CDT (0849 UT). The event was 81 km (50 mi) north of Jonesboro AR and about 15 km (9 mi) north of Pocahontas, AR. The magnitude was 3.1Lg.

Preliminary Source Parameters

• Date: 99/10/21
  
• Time(CDT): 03:49
  
• Latitude: 36°30'N (36.4927 DD)
  
• Longitude: 91°8'W (-91.0217 DD)
  
• Depth: 11.79 km
  
• Magnitude (MbLg) = 3.1
  

These are preliminary locations and magnitudes determined from data provided by the Cooperative New Madrid Seismic Network and the U.S. Geological Survey. Magnitude and location may change slightly as more data become available. Stay tuned as we will be adding more information.

Click here for an image of the ground motion as recorded by a seismometer at in Shelby Forest just north of Memphis, TN. The sensor is extremely sensitive (this recording only represents ground motion on the order of a few microns; the smallest dust particles are on the order of hundreds of microns) so while the motion may look dramatic, it may not be felt by humans more than a few miles from the epicenter.

Thus far, three monitoring stations are up and running at Attica and Warm Springs in Arkansas and Doniphan in Missouri. Click here for a map of these locations.