To construct a model for diverse seismic phenomena, first of all, we need to clarify what happened at the source. Especially we have to grasp slow earthquake activity because it has ambiguous signals.

① Precise location of deep tectonic tremor ： Yabe and Ide (2013, EPS)

In seismic signals of tectonic tremor, arrivals of P- and S-wave are ambiguous and successive. Hence, precise location itself is difficult for slow earthquake, especially in depth. Because hypocentral location of events is a fundamental information for following advanced analysis, we need to estimate them accurately. I have estimated the depth of tectonic tremor accurately with a method stacking many waveform correlation function in different time windows.

② Quntification of deep tectonic tremor activities ： Ide and Yabe (2014, GRL), Idehara et al. (2014, EPS), Yabe and Ide (2014, JGR), Ide et al. (2015, GRL), Yabe et al. (2015, JGR)

Characteristic of earthquake differs among every event. However, a group of earthquakes (seismicity) has a statistical nature. I have quantified activities of deep tectonic tremor in various subduction zones from diverse aspects,

which has revealed the spatial heterogeneity of their activities. Several correlations have been identified in the spatial variations of characteristics, which becomes a constraint on a physical model of slow earthquake.

③ Moment tensor estimations for deep LFEs

The moment tensor is a fundamental property of the seismic phenomena, which expresses the size of the event and the geometry of the fault. However, its estimation for LFEs or small earthquake is difficult because seismic waves with higher frequency than 1 Hz dominate. High-frequency seismic waves are sensitive to small-scale perturbations of the seismic velocity structure. Therefore, the modeling of such high-frequency waveform is difficult. But, recent advances in high performance computing enables us to calculate seismic waveforms with small-scale perturbations in the seismic velocity structure. I am conducting synthetic tests to evaluate how much seismic waveforms of LFEs are affected by the small-scale perturbations in the seismic velocity structure. Moment tensors of LFEs will be estimated with this method after the synthetic tests. Because geologic observations of ancient slow earthquake source insist the existence of brittle fractures oblique to the shear zone and the opening components in the fracture. Such observations should be compared with the moment tensor estimations.

④ Quntification of shallow tectonic tremor activities ： Yabe et al. (2019,JGR)

Slow earthquake occurs around the trench as well. This shallow slow earthquake occurs in much different condition (temperature, pressure, etc.) from the deeper counterpart. Therefore, differences and common points between shallow and deep slow earthquake should be a clue to understand the physical mechanism of slow earthquake. Although shallow slow earthquake is difficult to monitor because it occurs off shore, ocean bottom seismic networks (such as DONET in Nankai subduction zone) are maintained. Seismic data of such networks are utilized to quantify shallow tectonic tremor activities.