Earthquake Research Unbound by Existing Frameworks Overview of Source Process and Source Inversion Research
A dynamic seismology that continuously updates theories and models, driven by observational data.
Earthquakes are often regarded as well-understood phenomena.
However, the observational data tells a different story.
We confront the "unexplained earthquakes" revealed by data.
Earthquakes are rupture phenomena occurring deep underground.
Their true nature is accurately observed worldwide as seismic waves generated by fault slips. Even a moderate magnitude 6 earthquake is clearly recorded on the opposite side of the globe.
Our research does not start by asking, "Can this be explained within existing frameworks?" Instead, our starting point is what the observational data is telling us. Seismic waves contain not only information about the underground structure but also the essential truth of "what happened at the source."
We are in an era where research institutions around the world routinely analyze and publish source models using seismic waves immediately after major earthquakes. However, the routinely used analytical methods and source models often fail to fully explain the observational data.
We believe that if the observational data cannot be explained, we should question the methods and models themselves.
"When underground structure is uncertain, theory must explicitly incorporate uncertainty."
"When fault geometry is uncertain, the source model must solve for it."
Through the development of such analytical methods, the diversity of earthquake phenomena that have been overlooked by conventional frameworks is gradually coming to light. Furthermore, if observational facts demonstrate that classical earthquake cycle models do not hold, we will actively communicate that conclusion to society.
We relish the moments when widely accepted "common sense" is shattered. Rather than chasing trending research topics, we aim to conduct research that creates "new dots" (points of origin) to change the era.
Selected Works
- Source inversion assuming unknown underground structure Yagi & Fukahata (2011, GJI)
- Flexible source model capable of estimating fault geometry Shimizu, Yagi et al. (2020, GJI), Shimizu, Yagi et al. (2021, GJI)
- Novel adaptive smoothing Yamashita, Yagi et al. (2022, GJI)
- Hybrid source imaging method Yagi et al. (2012, EPSL)
- Stable seismicity analysis method Kasahara, Yagi et al. (2016, SRL)
- First introduction of modeling errors into source inversion Yagi & Fukahata (2008, GJI)
- Breakdown of classical earthquake cycle models Yagi et al. (2025, Seismica)
- Boomerang earthquakes and ultra-fast ruptures Inoue, Yamaguchi, Yagi et al. (2025, Seismica)
- Tsunami earthquakes as superpositions of irregular ruptures Yamaguchi, Yagi et al. (2025, Sci. Rep.)
- Deep-focus earthquakes that suddenly become prone to rupture Suzuki & Yagi (2011, GRL)
- Multi-scale fault ruptures Yagi et al. (2023, Sci. Rep.)
- Coupled rupture of dip-slip and strike-slip faults Ohara, Yagi et al. (2023, PEPS)
- Conjugate fault ruptures Yamashita, Yagi et al. (2021, Sci. Rep.)
- Foreshocks occur quite frequently Tamaribuchi, Yagi et al. (2018, EPS)
- Foreshocks and slow ruptures Yagi et al. (2014, GRL)
- The 2011 Tohoku earthquake as a total strain release event Yagi & Fukahata (2011, GRL)
For a complete list of publications, please visit our Google Scholar page.