The Flores back-arc thrust fault is a major system of west–east trending

thrust fault A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks. Thrust geometry and nomenclature Reverse faults A thrust fault is a type of reverse fault that has a dip of 45 degrees or less. I ...

s that extend eastwards from west of

Lombok Lombok, is an island in West Nusa Tenggara province, Indonesia. It forms part of the chain of the Lesser Sunda Islands, with the Lombok Strait separating it from Bali to the west and the Alas Strait between it and Sumbawa to the east. It is rou ...

just south of where

Sunda Shelf Geology, Geologically, the Sunda Shelf () is a south-eastern extension of the continental shelf of Mainland Southeast Asia. Major landmasses on the shelf include the Indonesia, Indonesian islands of Bali, Borneo, Java, Madura Island, Madura, an ...

ends at

Bali Sea The Bali Sea (, ) is the body of water north of the island of Bali and south of Kangean Island in Indonesia. The sea forms the south-west part of the Flores Sea, and the Madura Strait opens into it from the west. Geography The Bali Sea is someti ...

, towards the islands of

Sumbawa Sumbawa, is an Indonesian island, located in the middle of the Lesser Sunda Islands chain, with Lombok to the west, Flores to the east, and Sumba further to the southeast. Along with Lombok, it forms the province of West Nusa Tenggara, but th ...

Flores Flores is one of the Lesser Sunda Islands, a group of islands in the eastern half of Indonesia. Administratively, it forms the largest island in the East Nusa Tenggara Province. The area is 14,250 km2. Including Komodo and Rinca islands ...

, and Alor, with a total length of at least 800 km., entering the

Weber Basin Location of the Banda Sea in Southeast Asia Weber Deep () is the deepest point in the Banda Sea off Indonesia. Weber Deep maximum depth is 7,351 meters, (24,117 feet, 4.56 miles). Banda Sea is connected to the Pacific Ocean, near the Maluku I ...

and Aru Basin adjacent

Sahul Shelf Geology, Geologically, the Sahul Shelf () is a part of the continental shelf of the Australia (continent), Australian continent, lying off the northwest coast of mainland Australia. Etymology The name "Sahull" or "Sahoel" appeared on 17th c ...

of the

Australian plate The Australian plate is or was a major tectonic plate in the eastern and, largely, southern hemispheres. Originally a part of the ancient continent of Gondwana, Australia remained connected to India and Antarctica until approximately when Indi ...

. The thrust faults are south- dipping and lie within the back arc region of the Sunda–

Banda Arc The Banda Arc (main arc, Inner, and Outer) is a dual chain of islands in eastern Indonesia that is around 2,300 km long. It is the result of the collision of a continent and an intra-oceanic island arc. The presently active volcanic arc is ...

, which is related to the ongoing

subduction Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at the convergent boundaries between tectonic plates. Where one tectonic plate converges with a second p ...

of the

beneath the Sunda and

Banda Sea plate The Banda Sea plate is a minor tectonic plate underlying the Banda Sea in southeast Asia. This plate also carries a portion of Sulawesi Island, the entire Seram Island, and the Banda Islands. Clockwise from the east it is bounded by the Bird's ...

s. The thrust fault system developed as a result of the onset of

continental collision In geology, continental collision is a phenomenon of plate tectonics that occurs at Convergent boundary, convergent boundaries. Continental collision is a variation on the fundamental process of subduction, whereby the subduction zone is destroy ...

continental crust Continental crust is the layer of igneous, metamorphic, and sedimentary rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as '' continental shelves''. This layer is sometimes called '' si ...

of the Australian plate reached the

Sunda Trench The Sunda Trench, earlier known as and sometimes still indicated as the Java Trench, is an oceanic trench located in the Indian Ocean near Sumatra, formed where the Australian- Capricorn plates subduct under a part of the Eurasian plate. It is l ...

. The eastern part of the fault system is also known as the Wetar thrust. Above the main thrust fault are a series of imbricate (overlapping) thrust faults. These imbricate thrust faults are shallower in depth than the main Flores thrust. Although the exact thrust faults have not been established, these faults were thought to be responsible for the 2018 Lombok earthquakes.

References

Seismic faults of Southeast Asia Thrust faults Seismic faults of Indonesia {{tectonics-stub