This study conducted a field survey and multiproxy analyses on sediment cores retrieved from the Kobatake-ike pond in Choshi City, Chiba Prefecture, Japan. Kobatake-ike pond is located at a high elevation (i.e., 11 m above present-day sea level) and faces the southern part of the Japan Trench. Three event sand layers were detected within the continuous mud and peat sequences of 3000 years. Based on the multi-proxy analyses, including mineralogical composition, diatom assemblages, and geochemical markers, these sedimentological events were associated with past tsunamis. The most recent event was a sandy layer and is attributed to the AD 1677 Enpo tsunami, which was reported by an earlier study conducted in the pond. Our results demonstrated that two older sand layers are associated with large tsunamis that struck the Choshi area in AD 896–1445 and in BC 488–AD 215. In addition, the age ranges of these events seem to overlap that of large earthquakes and tsunamis known from the central part of the Japan Trench. This implies a possible spatiotemporal relation of earthquake generations between the central and southern parts of the Japan Trench. However, since the error ranges of the ages of tsunami deposits at the southern and central parts of the Japan Trench are still large, further investigation is required to clarify the relations of large earthquakes in both areas.

这项研究对从日本千叶县Ch子市的Kobatake-ike池中回收的沉积物芯进行了实地调查和多代理分析。Kobatake-ike池塘位于海拔高处（即，比当前海平面高11 m），面向日本海沟的南部。在3000年的连续泥浆和泥炭序列中检测到三个事件沙层。基于多种代理分析，包括矿物成分，硅藻组合和地球化学标志物，这些沉积学事件与过去的海啸有关。最近的事件是一个沙层，归因于公元1677年的恩波海啸，该事件是由先前在池塘中进行的一项研究报道的。我们的结果表明，两个较旧的沙层与大海啸有关，这些海啸袭击了公元896–1445和公元前488–AD 215的Ch子地区。此外，这些事件的年龄范围似乎与已知的大地震和海啸重叠从日本海沟的中部。这暗示着日本海沟中部和南部地区之间地震发生的可能时空关系。但是，由于日本海沟南部和中部海啸沉积年龄的误差范围仍然很大，因此需要进一步调查以阐明这两个地区大地震的关系。这暗示着日本海沟中部和南部地区之间地震发生的可能时空关系。但是，由于日本海沟南部和中部海啸沉积年龄的误差范围仍然很大，因此需要进一步调查以阐明这两个地区大地震的关系。这暗示着日本海沟中部和南部地区之间地震发生的可能时空关系。但是，由于日本海沟南部和中部海啸沉积年龄的误差范围仍然很大，因此需要进一步调查以阐明这两个地区大地震的关系。