A transportable mb(Lg) scale for central Europe and implications for low-magnitude Ms-mb discrimination
A transportable mb(Lg) scale for central Europe and implications for low-magnitude Ms-mb discrimination
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DOI：
10.1111/j.1365-246x.2005.02663.x
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发表时间：
2005-10
影响因子：
2.8
通讯作者：
H. Patton;J. Schlittenhardt
中科院分区：
文献类型：
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作者：
H. Patton;J. Schlittenhardt
总结我们扩展了Nuttli的mb（Lg）方法，使用了噪声校正的均方根（rms）幅度和几何扩展的Δ−1依赖性。利用德国区域地震台网（GRSN）记录的欧洲中南部地震的Lg波，开发了一个mb（Lg）公式，该公式需要一个新的校准常数Crms，以使rms mb（Lg）与Nuttli基于第三峰值振幅的传统公式保持在相同的基线上。GRSN台站必须根据场地条件和Lg衰减进行校准。LgQ的横向变化在整个研究区域似乎是显着的，和区域Q模型，包括恒定的Q分区北，南和阿尔卑斯山中部的开发使用基于站间和两个事件，单站的方法测量。当绘制对表面波估计的Mw，均方根MB（Lg）测量在中欧被发现是一致的MW-MB（Lg）的关系，北美和南亚，从而支持我们的MB（Lg）公式的可移植性。Grafenberg阵列数据的频率波数处理，使我们能够提取瑞利波的小事件，和区域Ms测量使用马歇尔和Basham公式。我们的Ms-mb（Lg）关系延伸到Ms 2.5，并与包括美国西部在内的其他地区的观测结果一致。Ms-mb（Lg）观测的歧视潜力进行了检查，在现实的监测条件下，从地震数据推断的路径校正，并统一适用于自然源和爆炸。在这些条件下，对于大的NTS爆炸，mb（Pn，P）大于mb（Lg）;然而，P波的Ms-mb标度斜率比Lg波的更陡，NTS爆炸的Ms-mb观测收敛于mb 4附近。因此，考虑到测量误差和由于区域偏差而导致的mb（Pn）的额外不确定性，小幅度的Pn和Lg波的辨别潜力几乎没有差异。因此，基于Lg的区域Ms-mb判别式可能是首选，因为Lg波对小地震的可检测性更好。这些结果需要在其他试验场的爆炸中得到证实。与天文台的经验相比，区域Ms−mb观测将识别能力扩展到至少一个Ms单位的较低震级。
SUMMARY We have extended the mb(Lg) method of Nuttli using root-mean-square (rms) amplitudes corrected for noise and a Δ−1 dependence for geometrical spreading. Lg waves recorded on the German Regional Seismic Network (GRSN) for earthquakes in south-central Europe were used to develop an mb(Lg) formula requiring a new calibration constant Crms to keep rms mb(Lg) on the same baseline as Nuttli's traditional formula based on 3rd-peak amplitudes. GRSN stations had to be calibrated for site terms and for Lg attenuation. Lateral variations in LgQ appear to be significant across the study area, and a regional Q model consisting of constant-Q partitions north, south and in the central Alps was developed using measurements based on interstation and two-event, single-station methods. When plotted against surface wave estimates of Mw, rms mb(Lg) measurements in central Europe are found to be consistent with Mw–mb(Lg) relationships for north America and southern Asia, thus supporting the transportability of our mb(Lg) formula. Frequency–wavenumber processing of Grafenberg Array data enabled us to extract Rayleigh waves for small events, and regional Ms were measured using the Marshall and Basham formula. Our Ms–mb(Lg) relationship extends to Ms 2.5 and agrees well with observations in other regions including the western United States. The discrimination potential of Ms–mb(Lg) observations was examined under realistic monitoring conditions, where path corrections were inferred from earthquake data and applied uniformly to natural sources and explosions. Under these conditions, mb(Pn, P) are greater than mb(Lg) for large NTS explosions; however, Ms–mb scaling slopes are steeper for P waves than they are for Lg, and Ms−mb observations for NTS explosions converge near mb 4. Thus, allowing for measurement errors and additional uncertainty in mb(Pn) due to regional bias, there is little difference in the discrimination potential for Pn and Lg waves at small magnitudes. As such, a regional Ms−mb discriminant based on Lg might be preferred owing to the better detectability of Lg waves for small earthquakes. These results need to be confirmed for explosions at other test sites. Compared to teleseismic experience, regional Ms−mb observations extend the discrimination capability to lower magnitudes by at least one Ms unit.