September 24, 2013 Tsunami: Off Coast Gwadar, Pakistan

A new island emerged from the ocean offshore of the city of Gwadar, Pakistan, after a strong magnitude-7.7 earthquake shook the country this morning (Sept. 24). The mound appears to be 20 to 40 feet (6 to 12 m) high and 100 feet (30 m) wide, DIG Gwadar Moazzam Jah, a district police officer, told Pakistan's Geo News. It rose out of the sea at a spot located about 350 feet (100 m) from the coast, he said... A mud volcano is a likely possibility because Gwadar's coastline already has several of the gurgling, steamy cones, both onshore and at sea... And in 1945, the magnitude-8.1 Makran temblor triggered the formation of mud volcanoes offshore of Gwadar, according to a study on mud volcanoes in Pakistan published in 2005. A recent study in the journal Nature Geoscience also suggests the 1945 earthquake released tons of methane from the seafloor...But Geologist Dave Petley, a landslide expert, thinks the island's low, arcuate (or bow) shape - as seen in the few pictures released so far - suggests a rotational landslide, rather than a conical mud volcano.(reference #10751)

Three tide gauges and one DART station in the Arabian Sea observed the tsunami. (reference #10750)

A mud volcano caused an island which measured approximately 76 m long, 30 m wide and 18 m high to form in the Arabian Sea about 600 meters off the coast near Gwadar, Pakistan. A tsunami was recorded with the following maximum wave heights: 0.17 m at Chah Bahar and 0.09 m at Jask, Iran; 0.26 m at Muscat, Oman. (reference #1053)

This earthquake triggered a tsunami that was recorded by various sea-level tide gauges along the coastal regions of the Arabian Sea and tsunami buoys in the Arabian Sea[...]The sudden uplift of the mud island might have caused the tsunami generation, which was clearly mapped by the backward ray tracing technique in this case study. The sudden uplift of mud island or submarine slumping might have caused the tsunami generation, which could be clearly mapped by the backward ray tracing technique as admissible tsunamigenic source. (reference #12691)

The modest tsunami recorded at the buoy and at Muscat (Oman)and Chah Bahar (Iran) was generated not by slip on the megathrust or a related splay fault but on a fault within the Makran accretionary prism, which is being shortened and uplifted by subduction. (reference #12692)

Satellite images before and after the earthquake showed that a new island emerged from the sea bottom due to the shakings of this large Mw 7.7 earthquake (NASA 2013). The island is located 380 km away from the epicentre in the Arabian Sea with an almost circular shape and a surface diameter of around 70–100m […] The maximum slip on the fault surface was around 15m. The fault motions generated maximum vertical and horizontal surface displacements of around 1m. It is clear […] that the coseismic crustal deformation field is significant only far from the nearest coastline and, thus cannot be responsible for the observed tsunami […] As the tsunami was not generated by coseismic displacement, possibly it was triggered by submarine geological phenomena triggered by the earthquake. (reference #14036)