Non-Volcanic Tremors Along West Nusa Tenggara, Indonesia Triggered by Large Teleseismic Earthquakes

An advanced analysis was conducted on the triggered 'non-volcanic' tremors (NVT) around Tambora volcano in West Nusa Tenggara, Indonesia by 35 teleseismic earthquakes with a magnitude of at least seven and epicentral distance of over 1,000 km between 2020 and 2022. The waveform data were taken from the Indonesian Agency for Meteorology, Climatology and Geophysics (BMKG). The identification of triggered tremors was based on the visual detection of high-frequency bursts (1-10 Hz and 2–8 Hz) of non-impulsive and prolonged seismic energy, exhibiting coherence across multiple seismic stations and modulation by teleseismic surface waves. Among the 35 earthquakes studied, we identified four teleseismic events that triggered NVT in West Nusa Tenggara. The 2021 Mw 7.4 and Mw 8.1 Kermadec, 2021 Mw 7.3 Vanuatu and 2022 Mw 7.7 Papua New Guinea earthquakes have triggered NVT in this region. We use envelope waveform cross-correlation to locate tremors. The study revealed that amplitudes of surface waves play a crucial role in determining the triggering potential, with an observed triggering threshold of approximately 0.1 cm/s, or dynamic stress 7–8K Pa. The triggered tremors were initiated by Rayleigh surface waves. It has been observed that triggering potential is controlled by the peak ground velocity (PGV), frequency, and dynamic stress.

Keywords: Non volcanic tremor; triggering threshold; PGV; frequency; dynamic stress; envelope waveform. cross correlation