 The United States Geological Survey operates a series of strong motion stations in the Imperial Valley and while the majority of stations in the array recorded ground accelerations that were not unexpected , station number six registered an unusually high vertical component reading of 1.74g which , at the time , was the highest yet recorded as the result of an earthquake . One explanation of the anomaly attributed the amplification to path effects and a separate theory put forth described supershear effects that generated a focused pulse directly at the station . A later proposal stated that both multipath and focusing effects due to a " lens like effect " produced by a sedimentary wedge at the junction of the Imperial and Brawley faults ( under the station ) may have been the cause of the high reading . 
