1. Maximum Earthquake Size for Subduction Zones
Yan Y. Kagan and David D. Jackson
Dept. Earth and Space Sciences, UCLA, Los Angeles,
CA ,
Maximum Earthquake Size for Subduction Zones

2. Outline Maximum earthquake size estimates for subduction zones:
Historical method;
Statistical method;
Moment-conservation method: tectonic versus seismic moment rates – area- and site-specific.

4. Flinn-Engdahl seismic regions:
Why select them? Regions were defined before GCMT catalog started (no selection bias), and it is easier to replicate our results (programs and tables available).
Kagan (JGR, 1997) used these regions to estimate Mmax for several tectonic categories.

6. A log-likelihood map for the distribution of the scalar seismic
moment of earthquakes in the Flinn-Engdahl zone #19
(Japan--Kurile-Kamchatka)

7. Kagan’s [1999] hypothesis of uniform b still stands.
Review of results on spectral slope, b – Bird & Kagan, 2004
Although there are variations, none is significant with 95%-confidence.
Kagan’s [1999] hypothesis of uniform b still stands.

9. DETERMINATION OF MAXIMUM MOMENT CONCERVATION PRINCIPLE
(CORNER) MAGNITUDE:
MOMENT CONCERVATION PRINCIPLE
Seismic moment rate depends on 3 variables --
The number of earthquakes in a region (N);
The beta-value (b-value) of G-R relation;
The value of maximum (corner) magnitude.
Tectonic moment rate depends on 3 variables --
1. Width of seismogenic zone (W km);
2. Seismic efficiency coefficient (chi %);
3. Value of shear modulus (mu - 30GPa -- 49GPa).

10. Tectonic rate for /6/30 period is calculated by using Kagan (JGR, 1997) parameters: W=30 km, mu=30 GPa, chi=1.0.
Tectonic rate for /12/31 period is calculated by using Bird & Kagan (BSSA, 2004) parameters: W=104 km, mu=49 GPa, chi=0.5.

14. DETERMINATION OF MAXIMUM (CORNER) MAGNITUDE: SITE-SPECIFIC
MOMENT CONCERVATION PRINCIPLE
1. General (area-specific) distribution of the earthquake size, for the simplicity of calculations we take it as the truncated Pareto distribution.
2. Site-specific moment distribution – large earthquakes have a bigger chance to intersect a site, hence the moment distribution is different from area-specific.
3. Geometric scaling of earthquake rupture. Length-width-slip are scale-invariant, proportional to the cube root of scalar moment.
4. Earthquake depth distribution is different for small versus large shocks: at least for strike-slip earthquakes large events would penetrate below the seismogenic layer.
5. Most of the small earthquakes do not reach the Earth surface and therefore do not contribute to the surface fault slip.

16. Calculation of Mmax for fault slip

17. Calculation of Mmax for fault slip (cont.)
For Tohoku area site-specific calculations yield
Mmax estimates

18. END
Thank you