The National Disaster Warning centre (NDWC) Thailand, has defended its decision not to issue an early tsunami alert after the 8.4-magnitude earthquake off the west coast of Indonesia’s Sumatra Island on Wednesday evening. Instead, the NDWC made a broadcast three hours later telling people there was no cause for alarm. Centre chairman Smith Dharmasarojana said yesterday the delay was based on a thorough analysis of the situation. The NDWC decided against a sudden TV broadcast to warn people about a possible tsunami because it predicted the quake, which struck about 6.