USS Gridley (DLG-21) the "Spruance"-class destroyer to escort reflagged Kuwaiti oil tankers through the Strait of Hormuz during Operation Earnest Will. While homeward bound, transiting the South China Sea, "Gridley" rescued Vietnamese refugees sighted in a small boat off of the coast of Vietnam. A Vietnamese-speaking crewman aboard "Gridley" was able to translate for those rescued, facilitating the process. "Gridley" returned to San Diego in June 1989. On 17 October of that year, the ship's visit to Naval Station, Treasure Island, California, was interrupted by the 6.9 Loma Prieta earthquake that struck the San Francisco Bay area. "Gridley"s crew provided assistance to victims
Earthquake prediction of having observed such phenomena prior to an earthquake, no such phenomena has been shown to be an actual precursor. A 2011 review found the "most convincing" electromagnetic precursors to be ULF magnetic anomalies, such as the Corralitos event (discussed below) recorded before the 1989 Loma Prieta earthquake. However, it is now believed that observation was a system malfunction. Study of the closely monitored 2004 Parkfield earthquake found no evidence of precursory electromagnetic signals of any type; further study showed that earthquakes with magnitudes less than 5 do not produce significant transient signals. The "International Commission on Earthquake Forecasting for