Just to give you an indication of where this is. You'll note the island chain starting at the Andaman-Nicobar Island and ending in Sumatra (where the Earthquake that caused the 2004 Tsunami that wreaked havoc on this area originated)
Obviously a 4.0 earthquake will not cause a tsunami, but if this is an pre-shock, it might indicate that one may be coming in the next few months or years.