We investigate the dependence of event‐specific ground‐motion residuals in the Ridgecrest region, California. We focus on the impact of using either local (⁠ML⁠) or moment (⁠Mw⁠) magnitude, for describing the source scaling of a regional ground‐motion model. To analyze homogeneous Mw⁠, we compute the source spectra of about 2000 earthquakes in the magnitude range 2.5–7.1, by performing a nonparametric spectral decomposition. Seismic moments and corner frequencies are derived from the best‐fit ω−2 source models, and stress drop is computed assuming standard circular rupture model. The Brune stress drop varies between 0.62 and 24.63 MPa (with median equal to 3.0 MPa), and values for Mw>5 are mostly distributed above the 90th percentile. The median scaled energy for Mw<5 is −4.57, and the low values obtained for the Mw 6.4 and 7.1 mainshocks (−5 and −5.2, respectively) agree with previous studies. We calibrate an ad hoc nonparametric ML scale for the Ridgecrest region. The main differences with the standard ML scale for California are observed at distances between 30 and 100 km, in which differences up to 0.4 magnitude units are obtained. Finally, we calibrate ground‐motion models for the Fourier amplitude spectra, considering the ML and Mw scales derived in this study and the magnitudes extracted from Comprehensive Earthquake Catalog. The analysis of the residuals shows that ML better describes the interevent variability above 2 Hz. At intermediate frequencies (between about 3 and 8 Hz), the interevent residuals for the model based on Mw show a correlation with stress drop: this correlation disappears, when ML is used. The choice of the magnitude scale has an impact also on the statistical uncertainty of the median model: for any fixed magnitude value, the epistemic uncertainty is larger for ML below 1.5 Hz and larger for Mw above 1.5 Hz.

中文翻译：

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加利福尼亚Ridgecrest地区的局部和矩幅值分析：对事件间地面运动变异性的影响

我们调查了加利福尼亚州里奇克莱斯特地区特定于事件的地面运动残差的依赖性。我们专注于使用局部（⁠ML⁠）或矩（⁠Mw⁠）量级的影响，来描述区域地面运动模型的源比例。为了分析均质Mw ?，我们通过执行非参数频谱分解来计算大约2.5级至7.1级范围内的2000次地震的震源谱。地震矩和转折频率是从最佳拟合的ω-2源模型得出的，而应力降的计算是基于标准圆形破裂模型进行的。Brune应力降在0.62和24.63 MPa之间变化（中值等于3.0 MPa），并且Mw> 5的值大部分分布在第90个百分位以上。Mw <5的中位标度能量为-4.57，Mw <6.4和7的低值。1个主震（分别为-5和-5.2）与以前的研究一致。我们为Ridgecrest地区校准了一个特殊的非参数ML量表。在30至100公里之间的距离上可以观察到与加州标准ML标度的主要差异，其中差异可以达到0.4个数量级单位。最后，考虑到本研究得出的ML和Mw标度以及从《综合地震目录》中提取的震级，我们针对傅立叶振幅谱校准了地面运动模型。对残差的分析表明，ML更好地描述了2 Hz以上的事件间变异性。在中频处（大约3到8 Hz之间），基于Mw的模型的事件间残差显示出与应力下降的相关性：当使用ML时，这种相关性消失了。