Recent Advances in Tectonic Tremor Research

Since its discovery about 25 years ago, tectonic tremor has been identified in many subduction zones and transform plate boundaries worldwide, greatly advancing our understanding of regional tectonics and earthquake generation processes. Tremor detection and catalog construction continue to progress in many regions. In this presentation, I review recent advances made by our group over the past several years.

Regarding tremor detection methods, although the use of AI has become increasingly common, the envelope-based approach remains highly effective. The code developed by Mizuno and Ide (2019, EPS) is openly available on GitHub (https://github.com/not522/MizunoIde2019), and has facilitated new tremor detections in various regions. Using newly released continuous seismic data from Taiwan, Ide and Chen (2024, GRL) revealed extensive tremor activity beneath the Central Range. Azúa et al. (2025, GRL) demonstrated that tremor near the Chile Triple Junction occurs close to a slab window. Lu and Ide (2026, EGU) detected previously unrecognized tremor in California through a comprehensive analysis of statewide continuous seismic data, particularly near the Mendocino Triple Junction and the Big Bend of the San Andreas Fault. Although distinguishing tremor from regular earthquakes has long been difficult, Yano and Ide (2024, GRL) developed a clustering-based approach that discriminates tremor from ordinary earthquakes using waveform and hypocentral features.

Estimating source mechanisms is essential for assessing the tectonic roles of tremor. Since Ide and Yabe (2014), stacked tremor signals have been used to extract very low-frequency components and perform moment tensor analyses in several regions. This method becomes increasingly stable as more data accumulate. Utilizing a new Taiwan tremor catalog, Hua et al. (2026, Tectonophysics) showed that tremor beneath the Central Range exhibits reverse-faulting mechanisms consistent with active mountain building. Mechanism estimates near the Mendocino Triple Junction also suggest tremor occurring along the lateral surface of the subducting slab.

Probabilistic modeling of tremor occurrence is another important research direction. Ide and Nomura (2022, EPS) applied renewal processes to model tremor as a time series at a given location, but capturing the characteristic spatiotemporal migration of tremor required more complex models. Yano et al. (2026, JGR) developed a stochastic process model incorporating spatial interactions and demonstrated that it outperforms renewal-based models. Such standardized models provide a basis for relating tremor behavior to tectonic processes and for detecting anomalies in otherwise steady tremor activity.