洞穴次生碳酸盐沉积物在古地震研究中的应用[封面文章]

Application of cave secondary carbonate sediments to paleoearthquake research[Cover]

关键词:  古地震  洞穴沉积物  次生碳酸盐  石笋  U系测年

Key words:  paleoearthquake  speleothem  secondary carbonate  stalagmite  U-series dating

摘要:

地震灾害对人类生命财产安全构成了严重的威胁。但目前由于观测记录较短，难以准确揭示地震发生的规律。古地震研究主要根据地震活动在不同地质档案中留下的记录来重建区域地震活动历史，并以此来探索地震的孕发机制与重现期。洞穴次生碳酸盐连续性好、时间跨度大、分布广泛且可以使用精确的U系测年方法，能够记录地震造成的渗流路径改变、洞穴和石笋形态扭曲、破坏等信息，可以弥补其他载体在古地震研究中的信息缺失。文章从洞穴内地震证据的识别原理、方法和限制因素等角度，对洞穴次生碳酸盐在古地震研究方面的应用进行了综述，发现石笋生长轴的偏折、石笋倒塌再生以及洞穴内鹅管和流石等其他沉积物的破坏是重建古地震的有效手段，但难点在于如何区分洞穴次生碳酸盐破坏的原因。因此，建议未来洞穴古地震研究应与多种地质档案相互补充和验证，明确沉积物破坏机制，在地震多发区域集中进行精细化研究。

Abstract:

Background, aim, and scope Earthquakes rank among the most threatening natural disasters to human life and property. Although their frequency is relatively low compared to other natural hazards, destructive earthquakes often lead to severe loss of life and infrastructure. Modern instrumental earthquake records remain limited in duration, and reliable prediction continues to pose significant challenges. Effective earthquake forecasting or seismic zonation requires a thorough understanding of the spatiotemporal distribution and variation trends of seismic activity in a given region, including changes in paleoearthquake intensity and recurrence intervals. Reconstructing historical earthquake sequences can therefore yield critical insights into seismic patterns and future hazards. Cave secondary carbonate, which offer advantages such as precise U-series dating potential, long-term continuity, and stable depositional environments, represent valuable archives for investigating earthquake mechanisms, origins, and risk assessments. Materials and methods This study reviews the application of speleothem in paleoseismic research, with a focus on their formation principles, methods for identifying seismic evidence, and relevant dating techniques. We also evaluate potential factors that may affect the extraction of earthquake-related signals from these deposits. Results Several types of speleothem damage are identified as reliable indicators for reconstructing paleoearthquakes, including: deflection of stalagmite growth axes, collapse and subsequent regrowth of stalagmites, burial of broken stalactites and soda straws under flowstone, fracturing of speleothems, and in-cave fault displacements. Precise dating of stalagmites that exhibit earthquake-induced damage followed by regrowth is proposed as a robust method for identifying paleoseismic events. Nonetheless, a multi-proxy approach remains essential to fully reconstruct earthquake histories using speleothems. Discussion Non-seismic factors, such as human activities, glacial movement, floods, debris flows, gravitational collapses, rock creep, and groundwater erosion, can also damage cave carbonate sediments. Among these, human activities may represent a major cause of speleothem destruction. Although these processes can complicate the interpretation of seismic evidence, different damage types exhibit distinctive characteristics, making it possible to discriminate among them through careful analysis and thereby derive more reliable paleoseismic information. Conclusions Speleothem are capable of preserving evidence of seismic events over long timescales and can serve as excellent archives for reconstructing paleoearthquake histories, provided that the causes of speleothem damage are accurately determined. Recommendations and perspectives Future research in cave-based paleoseismology should focus on the following directions: (1) Given the significant overlap between global karst regions and seismic zones, studies should prioritize areas with high seismicity to improve earthquake prediction and hazard mitigation. (2) Cave paleoseismic records should be integrated with historical documents and other geological archives to facilitate cross-validation and complementary interpretation. (3) Methods should be refined to minimize the influence of non-seismic factors and to extract more precise earthquake parameters, such as magnitude, intensity, and peak ground acceleration.