Living on the Ring of Fire, earth tremors are a regular occurrence and usually not too troublesome in Bali. Somewhere in the archipelago, a volcano will be rumbling, but usually not in Bali. This image from Wikipedia, captures six active volcanoes in Eastern Indonesia:
The same shot taken today would have Gunung Agung (Mt Agung) steaming away. Dominating eastern Bali, and visible from many parts of the island on a clear day, the sacred mountain, home to the mother temple, Pura Besakih, has been simmering for the past couple of weeks. Alert levels have risen dramatically in the past few days and are now sitting at level 3
We need to be wary without panicking, and plans are already in place to evacuate up to
50000 [update: 190,000] people at short notice should activity increase. The Balinese equivalent of the Red Cross has been gathering equipment, supplies and temporary accommodation. Reports are coming from the mountain of gas and strong sulphur fumes, and the exclusion zone has been extended to 7.5 kilometers. Nobody wants a repeat if the 1963 disaster
and all hope that Agung is just restless and will soon go back to sleep.
Communication is certainly more sophisticated than it was 54 years ago, and should the worst occur, casualties should be minimised as long as people heed the authorities. The damage of 1963 can still be seen on any trip to east Bali. More than 1000 people lost their lives and entire villages were wiped out. Tirta Gangga Water Palace was very badly damaged and needed extensive rebuilding.
This same area looks likely to be the most badly affected again but the entire island will be hit by ash and there will be major disruption to air traffic. A considered article about the current situation can be found in The Conversation.
I know 1963 also inspired at least one novel, The Night of Purnama by Anna Mathews, published 20 years after the event. It is long out of print, but might be available in used book stores.
We can only watch and wait.