An earthquake occurred at approximately 2338 UTC on July 20, 1991 (1838 CDT), in the vicinity of Falls City, Texas (Fig. 1), a small community situated about 67 km southeast of San Antonio. Using observations from ALQ, ATX, GOL, TUL and VVO, the NEIS reported a preliminary location of 29.0N 98.1W, and a body wave magnitude (mb) of 3.6, with no instrumentally measured focal depth. ATX (Austin, Texas) was the closest station. To determine the extent and intensity of the felt area of this earthquake, we published an earthquake questionnaire in the Karnes City Citation, the local newspaper, and one of us (Daniel Olson) personally interviewed people in Falls City and the surrounding area. All felt reports collected formed the basis for determining the felt area of this event (Figure 1). These reports varied from not felt, to felt and accompanied with loud noise, such as an explosion or a sonic boom. The felt area centered approximately on Falls City (29.0N, 98.0W), 11 kilometers east of the NEIS preliminary location. The felt area was oblong in shape, trending northeast-southwest, parallel to the Karnes and Wilson county line. The area of Modified Mercalli intensity IV felt reports covered 75 square km, and might have been large as 250 square km, if we include sparsely populated areas north and west of Falls City. For either 75 or 250 square km, the Nuttli et al. (1979) relation between intensity IV felt area and mb is consistent with mb of only 3.0 or less. . . .