We have computed synthetic Wood-Anderson seismograms for over 1100 arrivals at 10 three-component, broadband digital stations in the UNR western Great Basin-eastern Sierra Nevada network. These represent all the available records from local earthquakes over magnitude 3.5 between 1990 and June of 1993, plus selected events of smaller magnitude. There were 77 events ranging in magnitude from 2.2 to 5.9, including four events over magnitude 5. The distances considered ranged from 15 to 600 km, with the best-represented range being from 30 to 450 km. We invert these measurements to determine distance and station corrections appropriate for a local-magnitude scale, constrained by Richter's original definition that an earthquake of ML = 3 will cause a 1-mm zero to peak deflection of the Wood-Anderson seismogram at 100 km from the epicenter. The results between 30 and 450 km were essentially independent of choice of curve-fitting parameters. In the 30- to 500-km distance region, the smooth distance-correction curves were very similar to that determined by Richter (1958), which is still used for southern California earthquakes. We propose to use Richter's distance-correction curve in reporting amplitude magnitudes from our digital network.

We calibrate the local magnitude (ML) scale in southern Kansas, a region of increased seismicity due to oil and gas activities, using both an empirical and a synthetic approach to derive the attenuation curve. In the empirical approach, we use the classic Richter (1935)logA0 attenuation model to calculate ML using amplitude data from the southern Kansas Network catalog and calibrate it using moment magnitudes (Mw) from St. Louis University moment tensor solutions and Trugman et al. (2017). In the synthetic approach, we utilize a crustal velocity model to generate synthetic seismograms from which we measure amplitudes to estimate the attenuation curve. This second approach presents a novel way to calibrate ML, in any region of interest, when earthquake data are scarce or unavailable. Both approaches show lower attenuation in southern Kansas than in the relations being used by the U.S. Geological Survey and Oklahoma Geological Survey to compute ML values in this area. This difference results in a systematic decrease of ∼0.1 magnitude unit between our results and those reported in the southern Kansas Network catalog. We also find a dependence of ML on stress drop for earthquakes with corner frequencies near and below the Wood–Anderson instrumental corner of 1.25 Hz. The derived attenuation curve is consistent with a mean stress drop of 3–4 MPa for these earthquakes.

The method for generating maximum amplitude and signal to noise ratio values by using second order high pass Butterworth filter on local seismic magnitude scale calculations is proposed. The test data are signals from local earthquake that have been occurred in Sunda Strait on April 8th 2012. Based on the experimental results, a 8 Hz cutoff frequency and a gain of 2200 of second order Butterworth high pass filter as an approach to simulating the frequency response of Wood Anderson seismometer can provide maximum amplitude value, SNR, and the magnitude better than simulated Wood Anderson frequency response.

The Local Magnitude (ML), was the earliest proposed magnitude scale, allows for rapid determination based on observed amplitudes and a zero magnitude reference amplitudes (A0) derived from local events. However, the amplitudes are susceptible to external factors, the physically robust Moment Magnitude (Mw) was proposed. The previous studies showed a 1:1 relationship between ML and Mw for ML < 6.5 in Southern California; however, ML in Taiwan tend to overestimate when compare to Mw due to different regional attenuation characteristics. Although the previous study has recalibrated the logA0 attenuation model for shallow earthquakes in Taiwan, deep events exhibit an even more significant overestimation, averaging overestimate 0.528. Therefore, this study aims to discuss deep earthquakes in the Taiwan and establish a new logA0 attenuation model for deep events. Since models relying solely on hypocentral distance (R) result in depth-dependent residuals, a depth term (D) was incorporated to account for the physical characteristic of deep seismic waves often propagating through high-Q plates. The derived regression model is:logA0 = 0.097 - 1.587logR - 0.0014R + 0.417logD ± 0.273The results demonstrate that logA0 attenuation varies distinctly with distance at different depths, aligning with Richter mentioned that different depth events require distinct calibration. Furthermore, the logA0 value at a hypocentral distance 100 km differs from that of shallow event models, indicating the difference in attenuation properties. The recalibrated ML demonstrates no depth dependency and a consistent 1:1 relationship with Mw, with a standard deviation ±0.160. This study proposed model provides a rapid and precise ML calculation. This new model enhances the reliability of real-time hazard assessment and reduces magnitude conversion errors in catalog combination.