刘静,徐晶,偶奇,韩龙飞,王子君,邵志刚,张培震,姚文倩,王鹏. 2023. 关于1920年海原大地震震级高估的讨论. 地震学报,45(4):579−596. doi: 10.11939/jass.20220051
引用本文: 刘静,徐晶,偶奇,韩龙飞,王子君,邵志刚,张培震,姚文倩,王鹏. 2023. 关于1920年海原大地震震级高估的讨论. 地震学报,45(4):579−596. doi: 10.11939/jass.20220051
Liu J,Xu J,Ou Q,Han L F,Wang Z J,Shao Z G,Zhang P Z,Yao W Q,Wang P. 2023. Discussion on the magnitude overestimation of the 1920 Haiyuan earthquake. Acta Seismologica Sinica45(4):579−596. doi: 10.11939/jass.20220051
Citation: Liu J,Xu J,Ou Q,Han L F,Wang Z J,Shao Z G,Zhang P Z,Yao W Q,Wang P. 2023. Discussion on the magnitude overestimation of the 1920 Haiyuan earthquake. Acta Seismologica Sinica45(4):579−596. doi: 10.11939/jass.20220051

关于1920年海原大地震震级高估的讨论

Discussion on the overestimated magnitude of the 1920 Haiyuan earthquake

  • 摘要: 1920年海原大地震作为史料记载以来中国大陆震级最高、伤亡最多的极具破坏性的地震之一,开启了我国用现代地震学方法研究大地震的新篇章,在我国地震研究史上具有里程碑的意义。最新研究结果表明,1920年海原大地震的矩震级为MW(7.9±0.2),与文献和大众广泛接受的M8\raise0.5ex\hbox\scriptstyle 1\kern-0.1em/\kern-0.15em\lower0.25ex\hbox\scriptstyle 2 的数值相差较大。本文通过对震级标度及其演化历史的总结和梳理,阐述了仪器记录早期阶段基于地震波波形振幅和频率的震级标定存在系统偏差的问题,这与仪器限制、台站稀疏、标定不统一等因素有关,也使得1920年海原大地震和同时期世界上其它一些重要大地震的震级不同程度被高估。在各种震级标度中,矩震级MW与地震破裂面积和位移等物理参数关联,是地震震级的最佳标定方法。震级作为表述地震大小和能量的重要参数,被广泛地用于评估断层未来的地震潜势;震级的偏差对地震活动时空分布样式的研究会产生重要影响,并造成基于历史地震资料的地震危险性评价和灾害评估等产品的可信度降低。因此,本文倡导对历史地震震级进行检验和修订,并建议1920年海原大地震的震级采用矩震级MW(7.9±0.2)表示,修正后的1920年海原大地震的震级与2008年汶川地震(MW7.9,MS8.0)和2001年昆仑山大地震(MW7.8,MS8.1)相当。

     

    Abstract: The great 1920 Haiyuan earthquake, resulting in tremendous casualties, ranks as one of the largest and most devastating earthquakes in China. This significant event marks the start of investigating earthquakes through modern scientific approaches in China. Recent studies show that the moment magnitude of the 1920 Haiyuan earthquake is MW(7.9±0.2), prominently smaller than the widely known and often cited magnitude M8\raise0.5ex\hbox\scriptstyle 1\kern-0.1em/\kern-0.15em\lower0.25ex\hbox\scriptstyle 2 . This paper reviews the re-calibration and conversion of different types of magnitude in the early developing phase of seismometers and analogue seismographs. Similar to the 1920 Haiyuan earthquake, the magnitude of many large shallow earthquakes that occurred in this period are systematically overestimated due to factors such as developing technology, sparse instrumentation and data, and diverse calibration functions. The moment magnitude, linked to physical parameters of earthquake rupture, is the best magnitude scale. For magnitude is the most commonly used parameter in describing an earthquake’s size and energy and is an essential factor in seismic hazard assessment, bias and errors in magnitude conversion have significant consequences in understanding the spatio-temporal pattern of historical seismicity and the reliability of various products of seismic potential and hazard evaluation. We thus advocate citing revised moment magnitude MW(7.9±0.2) for the 1920 Haiyuan earthquake in future studies and re-evaluating the magnitude of historical earthquakes in general. With a revised magnitude, the 1920 Haiyuan earthquake is similar in size to the 2008 Wenchuan earthquake (MW7.9, MS8.0) and the 2001 Kunlun earthquake (MW7.8, MS8.1).

     

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