The Kelut result is more relieving for Java than it first may seem.

The Java arc (S.Sumatra @~Suoh region through to Sangeang Api) is a baclarc basin with a long interval time & is very close to its young's modulus (approaching a megathrust event) around about now.

The magma filled fractures incorporated into the base of the crust during the last megathrust event have now generally squeezed into the volcanoes with the result that the bulk of the volcanoes are now approaching dormancy & only the late stage volcanoes with long fracture sets are still historically active.

Activity at Kelut with a long history of activity resulting from squeezing in a gas rich magma filled fracture set is relieving as it means that there is still space in the arc to enable recompression. As the volcano is semi periodic it indicates that each eruption is the squeeze in of a newly mobilised fracture into the set indicating that shortening is possible @ the base of the crust.

Raung, Merapi, Semeru, & Krakatau also have periodic activity, however unlike Kelut most of these volcanoes may produce activity from compression of a magma chamber in the intermediate crust & do not indicate any further free space. Merapi may also have been an exception as the last eruption was fairly big & indicates a magma filled fracture may have been tapped @ the base of the crust.

While the javanese volcanoes remain active a major megathrust earthquake & bloody great big tsunami of 2004 size or bigger is unlikely. The late stage recompression thrusts in the central forearc rise are however able to give big enough tsunamis to remind the locals of what is coming later once the last of the java arc volcanoes shuts down.

Have a nice day: Ag