Research ArticleGEOPHYSICS

Global variations of large megathrust earthquake rupture characteristics

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Science Advances  21 Mar 2018:
Vol. 4, no. 3, eaao4915
DOI: 10.1126/sciadv.aao4915
  • Fig. 1 Map of seismic moment–scaled radiated energy variation for 119 global large megathrust earthquakes from 1990 to 2016.

    The radiated energy is based on the broadband source spectrum of the frequency band from 0.005 to 1 Hz. Stars indicate large tsunami earthquakes. The size of circles and stars is scaled with the earthquake magnitude.

  • Fig. 2 Examples of MRFs and REEF.

    (A and B) Examples of MRFs for earthquakes with high and low REEF values, respectively. (C) Observed radiated energy ER versus calculated minimum radiated energy ER_min for 119 global large megathrust earthquakes from 1990 to 2016. Red stars indicate tsunami earthquakes. The size of circles and stars is scaled with the earthquake seismic magnitude. Red, blue, and cyan circles are for three magnitude bins, Mw 8.0 to 9.2, 7.5 to 8.0, and 7.0 to 7.5, respectively. Three dashed lines show REEF values of 1, 10, and 100, respectively. The bottom right insert shows the parabolic shape of an MRF for minimum radiated energy for a given seismic moment and source duration. REEF varies from ~5 to 150 for all magnitude ranges considered.

  • Fig. 3 Comparison of REEF and other measures.

    Variation of REEF with (A) seismic moment–scaled radiated energy and (B) moment-scaled cubed source duration. Red stars indicate tsunami earthquakes (EQs). The size of circles and stars is scaled with the earthquake magnitude. Red, blue, and cyan circles are for three magnitude bins, Mw 8.0 to 9.2, 7.5 to 8.0, and 7.0 to 7.5, respectively. Variation of REEF values correlates with moment-scaled cubed duration, with little overall dependence on moment-scaled radiated energy, but REEF explicitly combines the radiated energy and source duration information to give a distinct measure of radiated energy variation between events.

  • Fig. 4 Map view of REEF values for 119 global large megathrust earthquakes.

    Earthquakes are color-coded by the corresponding REEF values in log10 scale. Note systematic REEF for some regions, such as high values for Colombia–Ecuador–Peru–northern Chile (N. Chile), northern Kurils (N. Kurils), Solomon Islands, and Sumatra and low values at southern Mexico (S. Mexico)–Middle America (M. America), southern Chile (S. Chile), northern Japan (N. Japan)–southern Kurils (S. Kurils), and central Aleutians (C. Aleutians). Stars are for large tsunami earthquakes. Two white circles show the 1960 Chile and 1964 Alaska earthquakes. Symbol sizes are scaled with earthquake magnitude.

  • Fig. 5 Schematic categorization of ruptures associated with varying REEF and RC values.

    Regions with slip patches of varying size and spacing, indicating variable fraction of asperity area RC, can have ruptures that either produce low REEF values (left side, with light shading indicating smooth, simple rupture) or produce high REEF values (right side, with dark shading indicating rough, complex ruptures). Individual slip patches may fail or they may trigger additional slip patches, which increases REEF and earthquake magnitude overall within either category. Rough regions are more likely to have compound rupture due to triggering with relatively larger increases in magnitude and REEF. Below each schematic, specific subduction zones and events in that category are listed. Earthquakes labeled in orange are dominated by the near-trench rupture. Labeled regions or earthquakes in parentheses lack REEF measurements but are assigned to categories based on qualitative rupture attributes. Kuril Is., Kuril Islands; Solomon Is., Solomon Islands.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/3/eaao4915/DC1

    section S1. Uncertainty in estimating seismic moment, source duration, radiated energy, and REEF

    section S2. Roughness of the MRF

    section S3. Possible geological factors

    fig. S1. Map of static stress drop estimates for 119 global large megathrust earthquakes.

    fig. S2. Map of seismic moment–scaled cubed source duration for large megathrust events.

    fig. S3. Map view of REEF estimates with the total duration assumed to be equal to 2Tc.

    fig. S4. Comparison of radiated energy for magnitude ~7.5 earthquake measured by different methods.

    fig. S5. Relative uncertainty estimation for radiated energy ER.

    fig. S6. Map view of REEF values and regional average.

    fig. S7. REEF versus MRF complexity, γ.

    fig. S8. Fraction of high-frequency (f >0.05 Hz) radiated energy plotted with earthquake magnitude.

    fig. S9. MRF (black) and corresponding minimum ER MRF (red) for 119 global large megathrust earthquakes.

    fig. S10. Comparisons between REEF and subduction zone parameters.

    table S1. Asperity size, spacing, and earthquake sizes for the modified asperity representation (Fig. 5).

    References (3243)

  • Supplementary Materials

    This PDF file includes:

    • section S1. Uncertainty in estimating seismic moment, source duration, radiated energy, and REEF
    • section S2. Roughness of the MRF
    • section S3. Possible geological factors
    • fig. S1. Map of static stress drop estimates for 119 global large megathrust earthquakes.
    • fig. S2. Map of seismic moment–scaled cubed source duration for large megathrust events.
    • fig. S3. Map view of REEF estimates with the total duration assumed to be equal to 2Tc.
    • fig. S4. Comparison of radiated energy for magnitude ~7.5 earthquake measured by different methods.
    • fig. S5. Relative uncertainty estimation for radiated energy ER.
    • fig. S6. Map view of REEF values and regional average.
    • fig. S7. REEF versus MRF complexity, γ.
    • fig. S8. Fraction of high-frequency (f >0.05 Hz) radiated energy plotted with earthquake magnitude.
    • fig. S9. MRF (black) and corresponding minimum ER MRF (red) for 119 global large megathrust earthquakes.
    • fig. S10. Comparisons between REEF and subduction zone parameters.
    • table S1. Asperity size, spacing, and earthquake sizes for the modified asperity representation (Fig. 5).
    • References (32–43)

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