The recompression of the Java backarc basin is in its late stage prior to a rebound/long duration, mercalli X event (r/lx) & bloody great big tsunami which relaxes the backarc basin out into the sea & lurches the unlocked Indo-Australasian plate under Java.
The event however while a natural consequence of recompression affecting the arc graben (where lusi is located), is not entirely a natural event as it would not have erupted if a gas well prospect was not present in the area @ the time of the Yogyakarta quake. It would however have erupted naturally within a century or so of this date.
A pretty good prospect for discovery of past r/lx timing in the java backarc basin would be 14C dating of the other mud volcano hills surrounding Lusi. There should be 8 to 10 of them formed during the Holocene alone. These mud volcano hills should pop up when the recompression of the backarc basin becomes strong enough to invert the arc graben pushing the arc graben back up between the arc graben wall faults. The overpressured mud in the arc grabem sediment fill should pop out as an individual mud volcano long before the arc graben fill pops up tectonically.
Of interest here is also that the recompression of the arc will squeeze all magma filled fractures in the deep crust & upper mantle into the volcanoes. In the latest stage (as now) only the longest fractures remain and the volcanoes (Merapi, Semeru, Tengger, Kelut, Krakatau, etc.), are now intermittently active or otherwise forming dome/flow complexes as a result of compression of the base of the magma chamber. r/lx of the java backarc basin will likely occur once the volcanoes go dormant, usually when the deep crustal fracture squeezing magma into the base of the magma chamber is squeezed flat; (see Lamongan, & Guntur for a good example of recent dormancy).
NOTE: Magma filled fractures incorporated into the base of the crust since the last r/lx @ the Java backarc basin may remain disconnected from a volcano for centuries & will cool & exsolve gas in situ @ the base of the crust. Reconnection of an isolated gas rich magma filled fracture with a volcano will produce a spectacular eruption from any volcano in the arc that may (or may not) have been dormant through the historic record. Good examples of this are eruptions from Agung(1963), Krakatau(1883), and Tambora(1815);Also of note in this case were major eruptions @ other volcanoes such as Kelut, & Raung. Even now the last of the reconnections of magma filled fractures with volcanoes may not yet have taken place.
Lusi driven by continued compression via vibrational break in of overpressured mud into the old gas prospect well will continue to erupt off & on until r/lx takes place, & may reactivate to quite high levels when another quake compresses the arc graben @ the now dormant Arjuno-Welirang-Kelut sector. It started early via artificial intervention but having started will keep going until r/lx relaxes the arc graben.
Keep watching that space...
Have a nice day: Ag