Data Services Products: Aftershocks

Summary

Animations and figures of seismicity automatically generated following large global earthquakes (Mag > 7).

Description

Following all global earthquakes with magnitudes greater than 7, aftershock sequence animations and figures are automatically generated and made available in SPUD. The movies and figures are updated hourly for 10 days. Starting on August 1, 2020, events from the FDSN (USGS) and the GCMT catalogs are used in this product. Depending on type of plot or movie, marker colors refer to the event depth, number of days since the mainshock or total number of earthquakes. When available, GCMT magnitudes and reference origins are the preferred source. GCMT focal mechanisms are included in plots when they become available. Results are backfilled to 1980 using the GCMT catalog as reference.

The Aftershocks data product was initially released in December 2014 and was upgraded (R2) in August 2020 to enhance the plots and introduce additional animations and plots.

For each event, there will be:

  • an aftershock sequence animation
  • an aftershock sequence heatmap animation (when available)
  • a seismicity map spanning 3 days before to 10 days after the mainshock
  • a plot showing the distribution of aftershock magnitudes as time progresses
  • two plots showing distribution of aftershocks along each of the strikes given by the GCMT solution (when available)
  • two plots showing distribution of aftershocks with depth along each of the strikes given by the GCMT solution, when available (when available)

For the figures generated, the radius of aftershocks plotted decreases as mainshock magnitude decreases:
    Mag ≥ 9.0            1000 km
    9.0 > Mag ≥ 8.5     500 km
    8.5 > Mag ≥ 8.0     400 km
    8.0 > Mag ≥ 7.0     300 km
    7.0 > Mag ≥ 6.0     200 km
            Mag < 6.0     100 km

Example animations and figures:

location animation

heatmap animation



(left) event animation and (right) event heatmap animation: from a day before the mainshock to 10 days after the mainshock with colors fading over the course of one day. Click on an image to play the corresponding animation.

Alaska location plot
Aftershock map showing all events within 3 days before to 10 days after the mainshock.

Seismicity
Background seismicity is plotted for all events previous to the mainshock within 100 km depth and 300 km radius.



Strike 1
Aftershocks are plotted based on their closest point to a line given by the strike in nodal plane 1 in the GCMT solution. This is only produced if a GCMT solution is available.
 

Strike 2
Aftershocks are plotted based on their closest point to a line given by the strike in nodal plane 2 in the GCMT solution. This is only produced if a GCMT solution is available.



Strike 1 vs depth
Aftershocks are plotted based on their closest point to a line given by the strike in nodal plane 1 in the GCMT solution vs their depth.
 

Strike 1 vs depth
Aftershocks are plotted based on their closest point to a line given by the strike in nodal plane 2 in the GCMT solution vs their depth.



Magnitude vs day
Magnitude versus time are plotted from three days before to 10 days after the mainshock. GCMT focal mechanisms are used, when available.
 
 
 
 

heatmap
Heatmap of events from three days before to 10 days after the mainshock. GCMT focal mechanisms are used, when available.


Citations and DOIs

To cite the IRIS DMC Data Products effort:

  • Hutko, A. R., M. Bahavar, C. Trabant, R. T. Weekly, M. Van Fossen, T. Ahern (2017), Data Products at the IRIS‐DMC: Growth and Usage, Seismological Research Letters, 88, no. 3, https://doi.org/10.1785/0220160190.

To cite the IRIS DMC Aftershocks data product or reference use of its repository:

To cite a particular Aftershocks data product via its DOI:
    – select the event of interest
    – click on Citations to obtain its DOI

References


United States Geological Survey (USGS)


Global CMT (GCMT) catalog:

  • Dziewonski, A. M., T.-A. Chou and J. H. Woodhouse, Determination of earthquake source parameters from waveform data for studies of global and regional seismicity, J. Geophys. Res., 86, 2825-2852, 1981. https://doi.org/10.1029/JB086iB04p02825

  • Ekström, G., M. Nettles, and A. M. Dziewonski, The global CMT project 2004-2010: Centroid-moment tensors for 13,017 earthquakes, Phys. Earth Planet. Inter., 200-201, 1-9, 2012. https://doi.org/10.1016/j.pepi.2012.04.002

Credits

  • Alexander Hutko

Timeline

2014-12-17
R1 Aftershocks online
2020-08-01
R2 Aftershocks online

Categories

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