Field Investigation of the November to December 2015 Earthquake Swarm in West Halmahera, Indonesia

The West Halmahera Swarm (WHS) event occurred from November to December 2015. A seismic station located in Ternate City detected at least 1000 shocks of magnitude (M) C 1 and 11 shocks of M C 4.5. Our estimation yields a cumula- tive seismic moment of 3.87 9 10²¹ N m, which is equivalent to a single M 8.3 earthquake. We conducted a field survey after the swarm event and found that roads and residents’ houses experienced cracks, while some parts of buildings were destroyed during the event. We find that the 2015 WHS was located just below the Jailolo volcano and was strongly associated with volcanic activity.