An earthquake affected the island of Java, Indonesia on 22 January 1780. The source and magnitude of the earthquake remains debated among seismologists. Proposed origins of the earthquake include shallow inland back-arc thrusting along a fault located within the upper crust on the island or rupture of the subduction zone off the southern coast of Java. The magnitude of the earthquake is estimated to be at least 8.5, while other sources usually refer to it with a range of Mw  8.0 to 8.5 for the megathrust earthquake. For the shallow crustal earthquake source, the magnitude range is Mw  7.0 to 8.0.