地震大小的度量

本文首先对地震大小度量的研究历程作了简要回顾。在此基础上着重指出以下几点: ① 近几十年广泛使用的M_L、m_b(m_B)、M_S震级标度,作为对地震大小的度量,不仅都存在着“以偏概全”和“震级饱和”的问题,而且由于未充分顾及地震波衰减的区域差异,尤其台站场地对地震动放大作用的差异,因此都只是对地震大小的不精确的度量。 ② 地震矩M₀不仅物理含义明确,而且克服了M_L、m_b(m_B)、M_S震级标度所存在的各种问题,是最适合科学度量地震大小的物理量。为了继续延用“震级”这一术语,Kanamori定义了矩震级标度M_W,虽然其假定的前提条件仍有待研究,但也是对地震相对大小的较合理的度量。 ③ 为更加科学地度量地震的大小,必须充分利用现代区域数字地震台网产出的大量波形数据,加强地震波衰减特征、场地效应和震源参数测定及有关定标关系的研究,在完善M_L、m_b(m_B)、M_S震级测定方法的基础上,重点改进、完善M_W标度,逐渐推进以M_W作为统一度量地震相对大小的物理量,为地震科学研究和地震预测研究奠定更加坚实的基础。

Measuring the Earthquake Size

In this paper, the research history of earthquake size measurement was reviewed in the first place. And on this basis the following points were pointed out: ① In recent decades, the M_L, m_b (m_B), M_S magnitude scales were widely used as the measures of an earthquake size. However, they not only had " overgeneralization" or " magnitude saturation" problem, but also were just inaccurate measurement because of not fully taking into account the regional differences of seismic attenuation, especially the differences of the site response on the ground motion amplification. ② The seismic moment M₀ not only has clear physical meaning, but can also overcome many scaling problems of the M_L, m_b (m_B), M_S magnitudes. It is the most suitable physical parameter for measuring earthquakes scientifically. In order to continue the term of “magnitude”, Kanamori defined the moment magnitude scale M_W, although the prerequisite assumptions remain to be studied, it is still a reasonable measure of the relative size of the earthquake. ③ For measuring earthquakes more scientifically, we must make full use of a large number of waveform data by the modern regional digital seismograph network, and strengthen the research on seismic wave attenuation characteristics, site effects, the measurement of source parameters and related scaling relations. On the basis of improving measurement methods of the M_L, m_b (m_B), M_S, we should focus on improving M_W scale in order to gradually advance M_W as a unified physical quantity to measure the earthquake relative size, it would lay a more substantial foundation for research on earthquake science and earthquake prediction.