The earthquake that struck the coast of northern Japan is the nation's biggest on record, raising questions on how much the insurers will need to make payouts.

MS&AD Insurance Group , Japan's top non-life insurer, had 3.07 percent of its total premiums of 1.28 trillion yen ($15.6 billion) exposed to earthquakes in March 2010, Goldman said.

Tokio Marine Holdings Inc's exposure to earthquake-related premiums was 3.2 percent, or 35.2 billion yen, of its total premiums of 1.1 trillion yen, Goldman said.

NKSJ Holdings Inc had 1.28 trillion yen worth of premiums in total, of which 3.16 percent, or 40.5 billion yen, was for earthquakes, Goldman said.

The industry paid out 78.3 billion yen after the earthquake which hit the city of Kobe and the surrounding areas in 1995, Goldman's report said. That was its largest-ever quake-related payment.