"The tremors have occurred due to the underlying movement of rock materials in West Halmahera and the surroundings," Kustoro Hariyatmoko, head of the Ternate geophysics office, said here, Saturday.
Of the total, only 71 tremors were felt by the local inhabitants, he noted.
By taking into account the number, the tremors this year are more extreme in nature as compared to those in 2015, he pointed out.
These quakes did not consequently trigger a tsunami.
Reported by Karel A Polakitan