The Coda Calibration and Processing Tool: Java-Based Freeware for the Geophysical Community

2020 ◽  
Author(s):  
Kevin Mayeda ◽  
Rengin Gok ◽  
Justin Barno ◽  
William Walter ◽  
Jorge Roman-Nieves
Keyword(s):  
Seismic Energy ◽  
Corner Frequency ◽  
Measurement Information ◽  
Apparent Stress ◽  
Source Information ◽  
Source Discrimination ◽  
Radiated Seismic Energy ◽  
Source Spectra ◽  
Stable Source ◽  
Calibration Tool

<p>The coda magnitude method of <em>Mayeda and Walter</em> (1996) provides stable source spectra and moment magnitudes (<em>M</em><em><sub>w</sub></em>) for local to regional events from as few as one station that are virtually insensitive to source and path heterogeneity. The method allows for a consistent measure of <em>M</em><em><sub>w</sub></em> over a broad range of event sizes rather than relying on empirical magnitude relationships that attempt to tie various narrowband relative magnitudes (<em>e.g.,</em> <em>M</em><em><sub>L</sub>, M<sub>D</sub>, m<sub>b</sub></em>, etc.) to absolute <em>M</em><em><sub>w </sub></em>derived from long-period waveform modeling. The use of <em>S</em>-coda and <em>P</em>-coda envelopes has been well documented over the past several decades for stable source spectra, apparent stress scaling, and hazard studies. However, up until recently, the method requires extensive calibration effort and routine operational use was limited only to proprietary US NDC software. The Coda Calibration Tool (CCT) stems from a multi-year collaboration between the US NDC and LLNL scientists with the goal of developing a fast and easy Java-based, platform independent coda envelope calibration and processing tool. We present an overview of the tool and advantages of the method along with several calibration examples, all of which are freely available to the public via GitHub (https://github.com/LLNL/coda-calibration-tool). Once a region is calibrated, the tool can then be used in routine processing to obtain stable source spectra and associated source information (<em>e.g.</em>, <em>M</em><em><sub>w</sub></em>, radiated seismic energy, apparent stress, corner frequency, source discrimination on event type and/or depth). As more events are recorded or new stations added, simple updates to the calibration can be performed. All calibration and measurement information (<em>e.g.,</em> site and path correction terms, raw & measured amplitudes, errors, etc.) is stored within an internal database that can be queried for future use. We welcome future collaboration, testing and suggestions by the geophysical community.  </p>

scholarly journals Global patterns of radiated seismic energy and apparent stress

1995 ◽  
Vol 100 (B9) ◽  
pp. 18205-18228 ◽  
Author(s):  
George L. Choy ◽  
John L. Boatwright
Keyword(s):  
Seismic Energy ◽  
Apparent Stress ◽  
Radiated Seismic Energy ◽  
Global Patterns

Stress drop estimates for some aftershocks of the Ometepec, Guerrero, Mexico, earthquake of June 7, 1982

1987 ◽  
Vol 24 (8) ◽  
pp. 1727-1733 ◽  
Author(s):  
Cecilio J. Rebollar ◽  
Rosa M. Alvarez
Keyword(s):  
Stress Drop ◽  
Wave Attenuation ◽  
Seismic Energy ◽  
Coda Wave ◽  
Apparent Stress ◽  
Radiated Seismic Energy ◽  
Seismic Coda ◽  
Seismic Quality Factor ◽  
Single Station ◽  
Stress Drops

Brune's stress drop, apparent stress, and arms stress drop are estimated at a single station for 25 aftershocks of the Ometepec earthquakes (Ms = 6.9 and Ms = 7.0). The arms stress drops and apparent stresses are systematically smaller than Brune's stress drops. Stress drops from the root mean square of acceleration and apparent stress range from 0.01 to 10.2 bars (1 bar = 100 kPa) except for two values (21.4 and 33.0 bars). On the other hand, Brune's stress drops range from 0.6 to 239 bars. Seismic moments ranging from 0.5 × 1019 to 289 × 1019 dyn∙cm (1 dyn∙cm = 10 μN∙cm) were estimated for events with coda magnitudes between 0.6 and 2.2. Values of radiated seismic energy calculated by integration of the displacement spectra range from 2.5 × 1012 to 2.3 × 1016 dyn∙cm. The fmax values lie between 16 and 30 Hz. Seismic coda wave attenuation measured on narrow band-pass-filtered seismograms show a linear dependence of the seismic quality factor of the form [Formula: see text] in the range of frequencies from 3 to 24 Hz.

Rupture Characteristics and Bedrock Structural Control of the 2016 Mw 6.0 Intraplate Earthquake in the Petermann Ranges, Australia

2020 ◽  
Vol 110 (3) ◽  
pp. 1037-1045 ◽  
Author(s):  
Januka Attanayake ◽  
Tamarah R. King ◽  
Mark C. Quigley ◽  
Gary Gibson ◽  
Dan Clark ◽  
...  
Keyword(s):  
Structural Control ◽  
P Wave ◽  
Corner Frequency ◽  
Intraplate Earthquake ◽  
Wave Source ◽  
Rupture Plane ◽  
Australian Continent ◽  
Vertical Displacements ◽  
Source Spectra ◽  
Surface Observations

ABSTRACT The 20 May 2016 surface-rupturing intraplate earthquake in the Petermann Ranges is the largest onshore earthquake to occur in the Australian continent in 19 yr. We use in situ and Interferometric Synthetic Aperture Radar surface observations, aftershock distribution, and the fitting of P-wave source spectra to determine source properties of the Petermann earthquake. Surface observations reveal a 21-km-long surface rupture trace (strike=294°±29°) with heterogeneous vertical displacements (<0.1–0.96  m). Aftershock arrays suggest a triangular-shaped rupture plane (dip  ≈  30°) that intersects the subsurface projection of the major geophysical structure (Woodroffe thrust [WT]) proximal to the preferred location of the mainshock hypocenter, suggesting the mainshock nucleated at a fault junction. Footwall seismicity includes apparent southwest-dipping Riedel-type alignments, including possible activation of the deep segment of the WT. We estimate a moment magnitude (Mw) of 6.0 and a corner frequency (fc) of 0.2 Hz, respectively, from spectral fitting of source spectra in the 0.02–2 Hz frequency band. These translate into a fault area of 124  km2 and an average slip of 0.36 m. The estimated stress drop of 2.2 MPa is low for an intraplate earthquake; we attribute this to low-frictional slip (effective coefficient of friction >0.015) along rupture-parallel phyllosilicate-rich surfaces within the host rock fabric with possible additional contributions from elevated pore-fluid pressures.

Radiated seismic energy of earthquakes in the south–central region of the Gulf of California, Mexico

2018 ◽  
Vol 214 (2) ◽  
pp. 990-1003
Author(s):  
Raúl R Castro ◽  
Antonio Mendoza-Camberos ◽  
Arturo Pérez-Vertti
Keyword(s):  
Central Region ◽  
Gulf Of California ◽  
Seismic Energy ◽  
The South ◽  
Radiated Seismic Energy ◽  
South Central

The characteristic of source spectra and stress drop of earthquakes in the Bucaramanga nest

2020 ◽  
Author(s):  
Wenzheng Gong ◽  
Xiaofei Chen
Keyword(s):  
Focal Mechanism ◽  
Stress Drop ◽  
Source Parameters ◽  
Time Function ◽  
Corner Frequency ◽  
Ratio Method ◽  
Source Time Function ◽  
Spectra Analysis ◽  
Source Spectra ◽  
Very High

<p>Spectra analysis is helpful to understand earthquake rupture processes and estimate source parameters like stress drop. Obtaining real source spectra and source time function isn’t easy, because the station recordings contain path effect and we usually can’t get precise path information. Empirical Green’s function (EGF) method is a popular way to cancel out the path effect, main two of which are the stacking spectra method (Prieto et al, 2006) and the spectral ratio method (Viegas et al, 2010; Imanishi et al, 2006). In our study, we apply the latter with multitaper spectral analysis method (Prieto et al, 2009) to calculate relative source spectra and relative source time function. Target event and EGFs must have similar focal mechanism and be collocated, so we combine correlation coefficient of wave at all stations and focal mechanism similarity to select proper EGFs.</p><p>The Bucaramanga nest has very high seismicity, so it’s suitable to calculate source spectra by using EGF method. We calculate the source spectra and source time function of about 1540 earthquakes (3-5.7ml, 135-160km depth) at Bucaramanga nest in Colombia. Simultaneously we also estimate corner frequency by fitting spectral source model (Brune, 1970; Boatwright, 1980) and stress drop using simple model (Eshelby, 1957) of earthquakes with multiple station recordings or EGFs. We obtain about 30000 events data with 12 stations from National Seismological Network of Colombia (RSNC).</p><p>The result show that the source spectra of most earthquakes fitted well by omega-square model are smooth, and the source spectra of some have obvious ‘holes’ near corner frequency, and the source time function of a few earthquakes appear two separate peeks. The first kind of earthquakes are style of self-arresting ruptures (Xu et al. 2015), which can be autonomously arrested by itself without any outside interference. Abercrombie (2014) and Wen et al. (2018) both researched the second kind of earthquakes and Wen think that this kind of earthquakes are style of the runaway ruptures including subshear and supershear ruptures. The last kind of earthquakes maybe be caused by simultaneous slip on two close rupture zone. Stress drop appear to slightly increase with depth and are very high (assuming rupture velocity/s wave velocity is 0.9). We also investigate the high-frequency falloff n, usually 2, of Brune model and Boatwright model by fitting all spectra, and find that the best value of n for Boatwright model is 2 and for Brune model is 3.5.</p>

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