古地震学:活动断裂强震复发规律的研究

古地震学是活动构造学、地震地质学和构造地貌学相结合的一个分支学科,它以野外工作为基础,以史前地震的发生位置、时间及震级为研究目标,其核心是古地震事件变形的地层和地貌证据。古地震学通过运用沉积地层学、地貌学和构造地质学等研究中常用的方法和手段来识别第四纪沉积中保存的史前强震的证据并对其进行准确年代测定,弥补了历史地震和仪器记录短而大地震原地复发间隔长的局限,获得活动断裂上多次强震的时空重复特征,为评估未来地震发生概率提供基础数据。本文对古地震学的历史、研究前沿和发展趋势进行综述。首先介绍了古地震学的定义、世界和中国古地震研究的发展历史和古地震研究中的基本研究方法,重点对古地震研究的最新进展和前沿领域,如古地震探槽方法的更新、古地震事件识别证据的分级和不确定性量化评估、古地震数据对地震复发间隔和同震位移的重复规律等理论认识的贡献以及基于震害效应的古地震研究等方面的重要研究成果进行了回顾,最后对古地震研究的未来发展趋势进行了展望,认为未来古地震研究中应加强地震事件识别证据的不确定性量化方法应用,在新的测年方法上开展探索,尝试和完善虚拟现实场景下的古地震研究。在中国,尤其像华北这样历史地震文献资料较为丰富的地区,历史地震震害记录与古地震探槽开挖的结合可以拓展震例研究的丰富程度,拓宽研究思路和方法,促进对难点地区活动断裂的古地震和区域地震危险性评价工作。

Paleoseismic investigation of the recurrence behavior of large earthquakes on active faults

Paleoseismology is a subdiciplinary study closely linked to active tectonics, earthquake geology, and tectonic geomorphology. It is field-based, aiming to reconstruct the location, time, and magnitude of paleoseismic events through the detailed documentation of the deformations caused by the events. Paleoseismic studies utilize the methods and means commonly used in the study of sedimentary stratigraphy, geomorphology, and structural geology to identify the evidence of prehistoric strong earthquakes preserved in well-dated Quaternary deposits. The instrumental record of earthquakes is much shorter than their return time on faults. Paleoseismology thus extends the record, providing fundamental data constraints on the spatio-temporal repetition of earthquake ruptures on faults, and facilitates the evaluation of the probability of earthquakes and their hazards. In this paper, we review the history, frontier research results, and future directions of the field. We first introduce the principle of paleoseismology, the history of its developments in the world and in China, and the basic methods used in paleoseismic research. We then summarize recent progress and frontiers in paleoseismic research, including developing new trenching techniques, quantifying the robustness of evidence in event identification, revealing the pattern of paleo-earthquake recurrence and coseismic displacement, and exploring shaking-related effects such as paleo-liquefaction and paleo-landslides. Finally, we briefly outline some future trends in paleoseismology. In future, we should further strengthen the application of quantitative evaluation of the uncertainty in event identification, continuously explore new dating techniques, and experiment with paleoseismology in virtual reality settings. In China, especially in North China where there is a long and precious historical record of earthquakes, innovative approaches combining historical accounts of shaking-related damages and field trenching will be fruitful.