Hi Shan, my own records show that there were 3 precursor signals detected on April 10, 2002. And all 3 look to me like they were linked in some way with the following earthquakes (which actually occurred hours before the signals were detected):

2002/04/10 17:35:02 40.62N 127.20W 10.0 3.7 A OFF COAST OF N CALIFORNIA
2002/04/10 16:58:12 40.59N 127.36W 10.0 4.0 A OFF COAST OF N CALIFORNIA
(NEIS data)

Additionally, signals detected on both April 9 and 11 look to me like they were pointing to the location of that destructive April 12 earthquake in Afghanistan (50 to 100 reported fatalities so far).