9:00 AM - 9:15 AM
[SCG52-01] Inter-segment Tectonics in Subduction Zones: Linking Earthquakes, Volcanoes, and Geomorphology
Keywords:Subduction system, Segmentation, Segment interaction, interdiciplinary research
On March 11, 2011, the M9 Tohoku-Oki earthquake struck off the Pacific coast of northeastern Japan, marking the largest earthquake ever recorded in the region. Along the Japan Trench, fault segments (fault zones) had been categorized as M7.5-class earthquake sources, with the prevailing assumption that similar earthquakes would repeatedly occur within each segment. As a result, insufficient attention was given to the possibility of an M9 earthquake across multiple segments.
Such earthquake fault segments are observed in many subduction zones, including the source faults of the Tonankai and Nankai earthquakes along the Nankai Trough and the three seismic fault segments along the Hikurangi subduction zone off the North Island of New Zealand (NZ). Moreover, there are cases where massive earthquakes result from the interaction of multiple segments. In these subduction zones, a strong correlation is often observed between fault segmentation and factors such as the distribution of interplate coupling strength, the occurrence of slow earthquakes (slow slip events and tectonic tremors), and the distribution of inland volcanoes.
When viewed from a spatial scale perspective, subduction zones exhibit strikingly similar characteristics at segment boundaries, such as the subduction of seamounts. This suggests that the various responses to plate subduction—ranging from the occurrence of great earthquakes on time scales of 100–1,000 years, the formation of volcanoes over 10,000–1,000,000 years, and the evolution of topography over 10 million–100 million years—could be understood as part of a unified subduction system.
Achieving such a unified understanding requires the integration of studies on subduction zones across different disciplines, including seismology, volcanology, geomorphology, and geology. During the growth period of plate tectonics research (around the 1980s), studies with this broad perspective were actively conducted. However, as research in individual fields and regions has become more refined, holistic examinations have become less frequent.
With recent advancements in observation and analysis techniques—such as the development of offshore seismic and crustal deformation monitoring networks and three-dimensional wave propagation simulations using supercomputers—it is becoming possible to obtain high-resolution three-dimensional insights into fault slip and subsurface structural heterogeneity.
By bringing together the latest research findings from various disciplines, including seismology, volcanology, and geodesy, this session aims to promote a comprehensive and interdisciplinary approach to understanding the factors behind segment formation, the interactions between segments, and the correlations between seismic fault segments, volcanic distributions, and geomorphological structures from offshore to onshore areas.
Such earthquake fault segments are observed in many subduction zones, including the source faults of the Tonankai and Nankai earthquakes along the Nankai Trough and the three seismic fault segments along the Hikurangi subduction zone off the North Island of New Zealand (NZ). Moreover, there are cases where massive earthquakes result from the interaction of multiple segments. In these subduction zones, a strong correlation is often observed between fault segmentation and factors such as the distribution of interplate coupling strength, the occurrence of slow earthquakes (slow slip events and tectonic tremors), and the distribution of inland volcanoes.
When viewed from a spatial scale perspective, subduction zones exhibit strikingly similar characteristics at segment boundaries, such as the subduction of seamounts. This suggests that the various responses to plate subduction—ranging from the occurrence of great earthquakes on time scales of 100–1,000 years, the formation of volcanoes over 10,000–1,000,000 years, and the evolution of topography over 10 million–100 million years—could be understood as part of a unified subduction system.
Achieving such a unified understanding requires the integration of studies on subduction zones across different disciplines, including seismology, volcanology, geomorphology, and geology. During the growth period of plate tectonics research (around the 1980s), studies with this broad perspective were actively conducted. However, as research in individual fields and regions has become more refined, holistic examinations have become less frequent.
With recent advancements in observation and analysis techniques—such as the development of offshore seismic and crustal deformation monitoring networks and three-dimensional wave propagation simulations using supercomputers—it is becoming possible to obtain high-resolution three-dimensional insights into fault slip and subsurface structural heterogeneity.
By bringing together the latest research findings from various disciplines, including seismology, volcanology, and geodesy, this session aims to promote a comprehensive and interdisciplinary approach to understanding the factors behind segment formation, the interactions between segments, and the correlations between seismic fault segments, volcanic distributions, and geomorphological structures from offshore to onshore areas.