The 8.4–9.0 Mw Sanriku earthquake was a catastrophic seismic event that struck the northern Honshu region of Japan, particularly affecting the area around Sendai. Characterized by an extraordinarily powerful magnitude, the earthquake produced a tsunami that surged into coastal areas, inundating them with devastating force. The tsunami waves traveled several kilometers inland, resulting in severe damage to infrastructure and loss of life in the local population. Archaeological evidence and historical records indicate that the tsunami's reach altered landscapes and disrupted settlements along the Sanriku coast. Reports from the time, although lacking scientific accuracy, documented the calamity's impact on communities, highlighting the energy released by the earthquake and the subsequent waves that devastated coastal villages.

The geological context of the region is crucial to understanding this event. Honshu, situated on the Pacific Ring of Fire, is characterized by tectonic activity due to the subduction of the Pacific Plate beneath the North American Plate. This tectonic setting makes it prone to violent earthquakes and tsunamis. Ancient Japanese society, while lacking modern seismic instruments, was acutely aware of the natural disasters shaped by their environment. Local histories and oral traditions preserved memories of the earthquake and tsunami, which have been vital for understanding the long-term implications of such destructive events on human settlement and urban development in coastal areas. The seismic event not only impacted the immediate vicinity but also influenced disaster preparedness and response in future generations.

The repercussions of this natural disaster extended beyond immediate devastation, serving as a pivotal reference point for understanding tectonic activity and coastal vulnerabilities. Over centuries, the resilience of communities in the affected areas was tested as they adapted to the realities of living in a geologically active region. This event has been a subject of study for historians and geologists alike, who seek to comprehend and mitigate the risks associated with future seismic activity in the region.