 During two outings in late 1979 and early 1980 several researchers ( including Thomas H. Heaton and John G. Anderson ) examined the region near the New River and discovered ground disturbances that were related to the Brawley aftershock . Along the banks of the river the seismologists discovered sand boils , a newly formed pond , and an extension crack that was found to run 10 km ( 6 @.@ 2 mi ) near the south bank in an irregular and disconnected fashion from Brawley to Wiest lake . It was later discovered that the Brawley earthquake had an aftershock zone that matched the area of the disturbances . Accelerograms recorded from the nearby Del Rio Country Club also showed " clear and impressive evidence " of near field ground motions , which may have indicated nearby primary faulting . 
