scholarly journals Changes of Reporting Rates in the Southern California Earthquake Catalog, Introduced by a New Definition of ML

2010 ◽  
Vol 100 (4) ◽  
pp. 1733-1742 ◽  
Author(s):  
T. Tormann ◽  
S. Wiemer ◽  
E. Hauksson
Keyword(s):  
Southern California ◽  
Earthquake Catalog ◽  
Definition Of ◽  
Reporting Rates

Southern California Earthquake Data Now Available in the AWS Cloud

2021 ◽  
Author(s):  
Ellen Yu ◽  
Aparna Bhaskaran ◽  
Shang-Lin Chen ◽  
Zachary E. Ross ◽  
Egill Hauksson ◽  
...  
Keyword(s):  
Southern California ◽  
Data Availability ◽  
First Year ◽  
Earthquake Catalog ◽  
High Data ◽  
Seismic Waveform ◽  
Challenges And Opportunities ◽  
Amazon Web Services ◽  
Computationally Intensive ◽  
Earthquake Data

Abstract The Southern California Earthquake Data Center is hosting its earthquake catalog and seismic waveform archive in the Amazon Web Services (AWS) Open Dataset Program (s3://scedc-pds; us-west-2 region). The cloud dataset’s high data availability and scalability facilitate research that uses large volumes of data and computationally intensive processing. We describe the data archive and our rationale for the formats and data organization. We provide two simple examples to show how storing the data in AWS Simple Storage Service can benefit the analysis of large datasets. We share usage statistics of our data during the first year in the AWS Open Dataset Program. We also discuss the challenges and opportunities of a cloud-hosted archive.

A Retrospective Analysis of b-Value Changes Preceding Strong Earthquakes

2021 ◽  
Author(s):  
Nicolas D. DeSalvio ◽  
Maxwell L. Rudolph
Keyword(s):  
B Value ◽  
Earthquake Precursors ◽  
Earthquake Catalog ◽  
Traffic Light ◽  
Magnitude Distribution ◽  
Parameter Combination ◽  
Definition Of ◽  
Value Changes ◽  
Frequency Magnitude Distribution ◽  
Optimal Set

Abstract Earthquake precursors have long been sought as a means to predict earthquakes with very limited success. Recently, it has been suggested that a decrease in the Gutenberg–Richter b-value after a magnitude 6 earthquake is predictive of an imminent mainshock of larger magnitude, and a three-level traffic-light system has been proposed. However, this method is dependent on parameters that must be chosen by an expert. We systematically explore the parameter space to find an optimal set of parameters based on the Matthews correlation coefficient. For each parameter combination, we analyze the temporal changes in the frequency–magnitude distribution for every M ≥ 6 earthquake sequence in the U.S. Geological Survey Comprehensive Earthquake Catalog for western North America. We then consider smaller events, those with a foreshock magnitude as small as 5, and repeat the analysis to assess its performance for events that modify stresses over smaller spatial regions. We analyze 25 M ≥ 6 events and 88 M 5–6 events. We find that no perfect parameter combination exists. Although the method generates correct retrodictions for some M 5 events, the predictions are dependent on the retrospectively selected parameters. About 80%–95% of magnitude 5–6 events have too little data to generate a result. Predictions are time dependent and have large uncertainties. Without a precise definition of precursory b-value changes, this and similar prediction schemes are incompatible with the IASPEI criteria for evaluating earthquake precursors. If limitations on measuring precursory changes in seismicity and relating them to the state of stress in the crust can be overcome, real-time forecasting of mainshocks could reduce the loss of lives.

scholarly journals An updated and unified earthquake catalog from 1787 to 2018 for seismic hazard assessment studies in Mexico

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Rashad Sawires ◽  
Miguel A. Santoyo ◽  
José A. Peláez ◽  
Raúl Daniel Corona Fernández
Keyword(s):  
Seismic Hazard ◽  
Hazard Assessment ◽  
Seismic Hazard Assessment ◽  
Large Earthquake ◽  
Seismic Source ◽  
Earthquake Catalog ◽  
Magnitude Conversion ◽  
Seismic Source Models ◽  
Source Models ◽  
Definition Of

Abstract Here we present a new updated and unified Poissonian earthquake catalog for Mexico. The details about the catalog compilation, the removal of duplicate events, unifying the magnitude scales, removal of dependent events through the declustering process and its completeness analysis are presented. Earthquake and focal mechanism data have been compiled from various local, regional and international sources. Large earthquake events (MW ≥ 6.5) have been carefully revised for their epicentral locations and magnitudes from trusted publications. Different magnitude-conversion relationships, compatible with available local and regional ones, has been established to obtain unified moment magnitude estimates for the whole catalog. Completeness periods for the declustered catalog were estimated for the definition of appropriate seismic source models for the whole territory. The final unified Poissonian earthquake catalog spans from 1787 to 2018, covering a spatial extent of 13° to 33°N and 91° to 117°W. This catalog is compatible with other published catalogs providing basis for new analysis related to seismicity, seismotectonics and seismic hazard assessment in Mexico.

Objective definition of rainfall intensity–duration thresholds for the initiation of post-fire debris flows in southern California

Landslides ◽  
2012 ◽  
Vol 10 (5) ◽  
pp. 547-562 ◽  
Author(s):  
Dennis M. Staley ◽  
Jason W. Kean ◽  
Susan H. Cannon ◽  
Kevin M. Schmidt ◽  
Jayme L. Laber
Keyword(s):  
Debris Flows ◽  
Southern California ◽  
Rainfall Intensity ◽  
Fire Debris ◽  
Definition Of

Archiving an Epidemic

2019 ◽  
Author(s):  
Robb Hernández
Keyword(s):  
Southern California ◽  
Chicano Art ◽  
Aids Crisis ◽  
Robert Mapplethorpe ◽  
David Hockney ◽  
Christopher Isherwood ◽  
And Performance ◽  
Definition Of

Archiving an Epidemic is the first book to examine the devastating effect of the AIDS crisis on a generation of Chicanx artists who influenced transgressive genders and sexualities operating in the Chicana and Chicano art movement in Southern California. From mariconógraphy to renegade street graffiti, from the Barrio Baroque to Frozen Art, these visual provocateurs introduced a radical queer languageemboldened by opportunities in LA’s art and retail culturein the 1980s. AIDS not only ravaged their lives, but also devastated their archives. A queer archival methodology is demanded to ascertain how AIDS and its losses and traumas have rearticulated recordkeeping practices beyond systemic forms of preservation. The resulting “archival bodies/archival spaces” of queer Chicanx avant-gardists Mundo Meza (1955–1985), Teddy Sandoval (1949–1995), and Joey Terrill (1955–present) refutes dismissive arguments that these provocateurs have had little consequence for the definition of the aesthetics of Chicano art and performance. With appearances by Laura Aguilar, Cyclona, Simon Doonan, David Hockney, Christopher Isherwood, Robert Mapplethorpe, and even Eddie Murphy, this book stands in defense of the alternative archivesthat emerged from this plague. Thinking outside traditional terms of institutional mediation, Archiving an Epidemic speculates not what Chicana/o art is but what it could have been.

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.

The ML scale in central California

1984 ◽  
Vol 74 (5) ◽  
pp. 1827-1843
Author(s):  
William H. Bakun ◽  
William B. Joyner
Keyword(s):  
Southern California ◽  
Body Wave ◽  
Horizontal Component ◽  
Parametric Form ◽  
Local Magnitude ◽  
Central California ◽  
Hypocentral Distance ◽  
Kronecker Delta ◽  
Definition Of ◽  
Homogeneous Media

Abstract Nine hundred fifty-seven maximum zero-to-peak Wood-Anderson amplitudes A (synthesized or recorded) from 40 horizontal-component seismographs (20 sites) with 0 ≲ Δ ≲ 400 km for 106 earthquakes with 18 ≦ log M0 ≦ 22.3 in central California have been fit in a least-squares sense using the parametric form log A ij = − n log R ij − K R ij − ∑ l = 1 40 S l δ ij + ∑ k = 1 106 C k δ ik where Aij = A (mm) for earthquake i on seismograph component j, δik = Kronecker delta, R = hypocentral distance, and n, K, Sl, and Ck are variables determined by regression analysis. The Ck are a magnitude measure, and the Sl are station corrections constrained to have zero average. We find n = 1.018 ± 0.107 and K = 0.00291 ± 0.00070 km−1. Setting n = 1, appropriate for body-wave propagation in homogeneous media, yields K = 0.00301 ± 0.00036 km−1. Following Richter's definition of an ML = 3 earthquake as one for which A = 1 mm at Δ = 100 km and S1 = 0, we express the local magnitude ML as ML = log A − log A0, where -log A0 = n log (R/100) + K (R − 100) + 3. For 30 ≲ Δ ≲ 475 km, the -log A0 values using n = 1 and K = 0.00301 km−1 are within 0.15 of Richter's values for southern California. For Δ ≲ 30 km, Richter's values are significantly smaller than those obtained here, a result consistent with recent studies of −log A0 for southern California. Our results suggest that the ML scale as commonly used underestimates the sizes of small shocks that are predominantly recorded at Δ ≲ 30 km.

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