Abstract
A reverse fault earthquake (Mw 7.1) occurred in the Northern Molucca Sea, Indonesia, on 15 November 2014 at 2:31:40 UTC. The earthquake produced small tsunami waves that are recorded at Jailolo (9 cm), Tobelo (1 cm), and Menado (3 cm) tide gauges. The Indonesian Agency for Climatology, Meteorology, and Geophysics (BMKG) issued a timely (5 minutes after the earthquake) tsunami warning for the event. We used the teleseismic double‐difference seismic tomography method (teletomoDD) to relocate the hypocenters of the mainshock and the aftershocks. The relocated hypocenter of the mainshock for the 2014 Northern Molucca Sea earthquake is located at 1.923°N, 126.539°E, and depth of 48.87 km. In general, the relocated aftershock hypocenters are shallower than those from the BMKG catalog. The relocated hypocenters are distributed within a depth range of 6 to 64 km. The aftershock area from the relocated hypocenters is 80 km long and 55 km wide. The estimated seismic moment from the Global CMT solution (GCMT) was 4.75 × 1019 Nm. We simulated the tsunami from fault model of each GCMT nodal plane to find a fault model that can best explain the observed tsunami heights at Jailolo, Tobelo, and Menado tide gauges. The best single fault model for this event is dipping to the west, has fault length, width, and slip amount of 47 km, 25 km, and 1.16 m, respectively. The K value calculated using the observed and simulated tsunami heights for this best model is 1.026, suggests a very good fit to tsunami observations.
Highlights
The Molucca Sea collision zone lies in the complex junction between large plates of Sunda, Australian, Pacific and Philippine Sea plates (Bird, 2003)
The relocated hypocenter of the mainshock for the 2014 Northern Molucca Sea earthquake is at 1.9014N, 126.5147E, and depth of 48.87 km. It was shifted from a deeper location of 1.95E, 126.490E, and depth of 60 km based on the BMKG catalog
There is no hypocenter from the BMKG catalog that has a depth shallower than 10 km
Summary
The Molucca Sea collision zone lies in the complex junction between large plates of Sunda, Australian, Pacific and Philippine Sea plates (Bird, 2003). Both Sangihe volcanic arc on the west and Halmahera arc on the east are active and convex toward the Molucca Sea (Silver and Moore, 1978). Islands has produced tsunamis from tsunamigenic earthquakes and volcanic eruptions as described in previous studies (Iida et al, 1967; Berninghausen, 1969). The relocated hypocenters distribution show reversed V-shape Molucca sea slab beneath the area subduct to the west and east direction (Yulianto et al, 2017; Nugraha et al, 2015; Shiddiqi et al, 2014). The initial tsunami warning was issued at 2:36:01 UTC or approximately 5 minutes after the earthquakes origin time, and the tsunami warning was terminated four hours later
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