Recalibration of the Local Magnitude (ML) Scale for Earthquakes in the Yellowstone Volcanic Region

2021 ◽  
Author(s):  
James Holt ◽  
James C. Pechmann ◽  
Keith D. Koper
Keyword(s):  
Broad Peak ◽  
Local Magnitude ◽  
Saint Louis ◽  
Hypocentral Distance ◽  
Saint Louis University ◽  
High Attenuation ◽  
University Of Utah ◽  
Volcanic Region ◽  
Station Corrections ◽  
Spatially Distributed

ABSTRACT The Yellowstone volcanic region is one of the most seismically active areas in the western United States. Assigning magnitudes (M) to Yellowstone earthquakes is a critical component of monitoring this geologically dynamic zone. The University of Utah Seismograph Stations (UUSS) has assigned M to 46,767 earthquakes in Yellowstone that occurred between 1 January 1984 and 31 December 2020. Here, we recalibrate the local magnitude (ML) distance and station corrections for the Yellowstone volcanic region. This revision takes advantage of the large catalog of earthquakes and an increase in broadband stations installed by the UUSS since the last ML update in 2007. Using a nonparametric method, we invert 7728 high-quality, analyst-reviewed amplitude measurements from 1383 spatially distributed earthquakes for 39 distance corrections and 20 station corrections. The inversion is constrained with four moment magnitude (Mw) values determined from time-domain inversion of regional-distance broadband waveforms by the UUSS. Overall, the new distance corrections indicate relatively high attenuation of amplitudes with distance. The distance corrections decrease with hypocentral distance from 3 km to a local minimum at 80 km, rise to a broad peak at 110 km, and then decrease again out to 180 km. The broad peak may result from superposition of direct arrivals with near-critical Moho reflections. Our ML inversion doubles the number of stations with ML corrections in and near the Yellowstone volcanic region. We estimate that the additional station corrections will nearly triple the number of Yellowstone earthquakes that can be assigned an ML. The new ML distance and station corrections will also reduce uncertainties in the mean MLs for Yellowstone earthquakes. The new MLs are ∼0.07 (±0.18) magnitude units smaller than the previous MLs and have better agreement with 12 Mws (3.15–4.49) determined by the UUSS and Saint Louis University.

scholarly journals The ML scale in Southern California

1987 ◽  
Vol 77 (6) ◽  
pp. 2074-2094
Author(s):  
L. K. Hutton ◽  
David M. Boore
Keyword(s):  
Southern California ◽  
Strong Motion ◽  
Body Waves ◽  
Local Magnitude ◽  
Hypocentral Distance ◽  
Station Corrections ◽  
Original Definition ◽  
Definition Of ◽  
Large Earthquakes ◽  
Distance Correction

Abstract Measurements (9,941) of peak amplitudes on Wood-Anderson instruments (or simulated Wood-Anderson instruments) in the Southern California Seismographic Network for 972 earthquakes, primarily located in southern California, were studied with the aim of determining a new distance correction curve for use in determining the local magnitude, ML. Events in the Mammoth Lakes area were found to give an unusual attenuation pattern and were excluded from the analysis, as were readings from any one earthquake at distances beyond the first occurrence of amplitudes less than 0.3 mm. The remaining 7,355 amplitudes from 814 earthquakes yielded the following equation for ML distance correction, log A0 − log A 0 = 1.110 log ( r / 100 ) + 0.00189 ( r − 100 ) + 3.0 where r is hypocentral distance in kilometers. A new set of station corrections was also determined from the analysis. The standard deviation of the ML residuals obtained by using this curve and the station corrections was 0.21. The data used to derive the equation came from earthquakes with hypocentral distances ranging from about 10 to 700 km and focal depths down to 20 km (with most depths less than 10 km). The log A0 values from this equation are similar to the standard values listed in Richter (1958) for 50 < r < 200 km (in accordance with the definition of ML, the log A0 value for r = 100 km was constrained to equal his value). The Wood-Anderson amplitudes decay less rapidly, however, than implied by Richter's correction. Because of this, the routinely determined magnitudes have been too low for nearby stations (r < 50 km) and too high for distant stations (r > 200 km). The effect at close distances is consistent with that found in several other studies, and is simply due to a difference in the observed ≈ 1/r geometrical spreading for body waves and the 1/r2 spreading assumed by Gutenberg and Richter in the construction of the log A0 table. ML's computed from our curve and those reported in the Caltech catalog show a systematic dependence on magnitude: small earthquakes have larger magnitudes than in the catalog and large earthquakes have smaller magnitudes (by as much as 0.6 units). To a large extent, these systematic differences are due to the nonuniform distribution of data in magnitude-distance space (small earthquakes are preferentially recorded at close distances relative to large earthquakes). For large earthquakes, however, the difference in the two magnitudes is not solely due to the new correction for attenuation; magnitudes computed using Richter's log A0 curve are also low relative to the catalog values. The differences in that case may be due to subjective judgment on the part of those determining the catalog magnitudes, the use of data other than the Caltech Wood-Anderson seismographs, the use of different station corrections, or the use of teleseismic magnitude determinations. Whatever their cause, the departures at large magnitude may explain a 1.0:0.7 proportionality found by Luco (1982) between ML's determined from real Wood-Anderson records and those from records synthesized from strong-motion instruments. If it were not for the biases in reported magnitudes, Luco's finding would imply a magnitude-dependent shape in the attenuation curves. We studied residuals in three magnitude classes (2.0 < ML ≦ 3.5, 3.5 < ML ≦ 5.5, and 5.5 < ML ≦ 7.0) and found no support for such a magnitude dependence. Based on our results, we propose that local magnitude scales be defined such that ML = 3 correspond to 10 mm of motion on a Wood-Anderson instrument at 17 km hypocentral distance, rather than 1 mm of motion at 100 km. This is consistent with the original definition of magnitude in southern California and will allow more meaningful comparison of earthquakes in regions having very different attenuation of waves within the first 100 km.

scholarly journals Attenuation relationships of peak ground motions in the Jazan Region

2021 ◽  
Vol 14 (3) ◽  
Author(s):  
Ali K. Abdelfattah ◽  
Abdullah Al-amri ◽  
Kamal Abdelrahman ◽  
Muhamed Fnais ◽  
Saleh Qaysi
Keyword(s):  
Saudi Arabia ◽  
Ground Motions ◽  
Prediction Equation ◽  
Peak Ground Velocity ◽  
Local Magnitude ◽  
Ground Acceleration ◽  
Data Set ◽  
Hypocentral Distance ◽  
Distance Range ◽  
Attenuation Relationships

AbstractIn this study, attenuation relationships are proposed to more accurately predict ground motions in the southernmost part of the Arabian Shield in the Jazan Region of Saudi Arabia. A data set composed of 72 earthquakes, with normal to strike-slip focal mechanisms over a local magnitude range of 2.0–5.1 and a distance range of 5–200 km, was used to investigate the predictive attenuation relationship of the peak ground motion as a function of the hypocentral distance and local magnitude. To obtain the space parameters of the empirical relationships, non-linear regression was performed over a hypocentral distance range of 4–200 km. The means of 638 peak ground acceleration (PGA) and peak ground velocity (PGV) values calculated from the records of the horizontal components were used to derive the predictive relationships of the earthquake ground motions. The relationships accounted for the site-correlation coefficient but not for the earthquake source implications. The derived predictive attenuation relationships for PGV and PGA are$$ {\log}_{10}(PGV)=-1.05+0.65\cdotp {M}_L-0.66\cdotp {\log}_{10}(r)-0.04\cdotp r, $$ log 10 PGV = − 1.05 + 0.65 · M L − 0.66 · log 10 r − 0.04 · r , $$ {\log}_{10}(PGA)=-1.36+0.85\cdotp {M}_L-0.85\cdotp {\log}_{10}(r)-0.005\cdotp r, $$ log 10 PGA = − 1.36 + 0.85 · M L − 0.85 · log 10 r − 0.005 · r , respectively. These new relationships were compared to the grand-motion prediction equation published for western Saudi Arabia and indicate good agreement with the only data set of observed ground motions available for an ML 4.9 earthquake that occurred in 2014 in southwestern Saudi Arabia, implying that the developed relationship can be used to generate earthquake shaking maps within a few minutes of the event based on prior information on magnitudes and hypocentral distances taking into considerations the local site characteristics.

The SAMP8 mouse as a model for Alzheimer disease: studies from Saint Louis University

2004 ◽  
Vol 1260 ◽  
pp. 23-28 ◽  
Author(s):  
J.E Morley ◽  
W.A Banks ◽  
V.B Kumar ◽  
S.A Farr
Keyword(s):  
Alzheimer Disease ◽  
Saint Louis ◽  
Saint Louis University ◽  
Samp8 Mouse

scholarly journals Validity of Computer Based Administration of Cognitive Assessments compared to Traditional Paper-based Administration

2020 ◽  
Author(s):  
Siao Ye ◽  
Brian Ko ◽  
Huy Phi ◽  
David Eagleman ◽  
Benjamin Flores ◽  
...  
Keyword(s):  
Neuropsychological Testing ◽  
Verbal Learning ◽  
Screening Tools ◽  
Cognitive Assessments ◽  
Saint Louis ◽  
Saint Louis University ◽  
Stroop Color Word Test ◽  
Computer Based ◽  
Highly Correlated ◽  
Composite Scores

Traditional pen and paper based neuropsychological tests (NPT) for cognition assessment have several challenges limiting their use. They are time consuming, expensive, and require highly trained specialists to administer. This leads to testing being available to only a small portion of the population and often with wait times of several months. In clinical practice, we have found results tend not to be integrated effectively into assessment and plans of the ordering provider. Here we compared several tests using BrainCheck (BC), a computer-based NPT battery, to traditional paper-based NPT, by evaluating individual tests as well as comparing composite scores to scores on traditional screening tools. 26 volunteers took both paper-based tests and BC. We found scores of four assessments (Ravens Matrix, Digit Symbol Modulation, Stroop Color Word Test and Trails Making A&B Test) were highly correlated. The Balance Examination and Immediate/Delayed Hopkins Verbal Learning, however, were not correlated. The BC composite score was correlated to results of the Saint Louis University Mental Status (SLUMS) exam [1], the Mini-Mental State Examination (MMSE) [2], and the Montreal Cognitive Assessment (MoCA). Our results suggest BC may offer a computer-based avenue to address the gap between basic screening and formal neuropsychological testing.

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