Yan Y. Kagan
Dept. Earth and Space Sciences, UCLA, Los Angeles,
CA 90095-1567, kagan@moho.ess.ucla.edu,
http://eq.ess.ucla.edu/~kagan.html
GLOBAL EARTHQUAKE
FORECAST
http://moho.ess.ucla.edu/~kagan/Potsdam2.pptx
Global forecast advantages:
• 1. High magnitude threshold (M=5.8). Fewer
volcanic and man-induced events, less
aftershocks (less than 25%).
• 2. High event rate – thus fast rigorous testing
(1 year or less).
• 3. High quality initial data – global catalogs
are more uniform and homogeneous.
• 4. Number degrees of freedom in forecast
model is small and well-controlled.
See also more extensive presentation:
http://moho.ess.ucla.edu/~kagan/Potsdam1.pptx
Earthquake Phenomenology
Modern earthquake catalogs include origin
time, hypocenter location, and second-rank
seismic moment tensor for each earthquake.
The DC tensor is symmetric, traceless, with
zero determinant: hence it has only four
degrees of freedom -- one for the norm of the
tensor and three for the 3-D orientation of the
earthquake focal mechanism. An earthquake
occurrence is considered to be a stochastic,
tensor-valued, multidimensional, point process.
World seismicity: 1976 – 2012
(Global Centroid Moment Tensor Catalog)
Statistical studies of earthquake catalogs
-- time, size, space, focal mechanism
• Catalogs are a major source of information on
earthquake occurrence.
• Since late 19-th century certain statistical
features were established: Omori (1894) studied
temporal distribution; Gutenberg & Richter
(1941; 1944) -- size distribution.
• Quantitative investigations of spatial patterns
started late (Kagan & Knopoff, 1980).
• Focal mechanism investigations (Kagan, 1982;
1991; 2009; 2012), Kagan & Jackson, 2014-5.
Advantages of
this distribution:
Simple (only one more parameter than G-R);
Has a finite integrated moment (unlike G-R) for b < 1;
Fits global subcatalogs slightly better than the gamma distribution.
Review of results on spectral slope, b:
Although there are variations, none is significant with 95%-confidence.
Kagan’s [1999] hypothesis of uniform b still stands.
Earthquake rate forecasting
• The fractal dimension of earthquake process is
lower than the embedding dimension: Space –
2.2 in 3D,Time – 0.5 in 1D.
• This allows us to forecast rate of earthquake
occurrence – specify regions of high
probability and use temporal clustering for
short-term forecast -- evaluating possibility of
new event.
• Long-term forecast: Spatial smoothing kernel
is optimized by using first temporal part of a
catalog to forecast its second part.
Kernel
optimi
zation:
I_0 vs
I_1
and
I_2
Forecast:
Long-term
earthquake
rate based on
GCMT
catalog 1977present.
0.1 x 0.1
degree,
Magnitude
M>=5.8
Forecast:
Short-term
earthquake
rate based on
GCMT
catalog 1977present.
0.1 x 0.1
degree,
Magnitude
M>=5.8
Error diagram tau,
nu for global longterm seismicity (M
> 5.0) forecast.
Solid black line -the strategy of
random guess.
Solid thick red
diagonal line is a
curve for the
global forecast.
Blue line is
earthquake
distribution from
the PDE catalog in
2004-2006
(forecast);
magenta line
corresponds to
earthquake
distribution from
the PDE catalog in
1969-2003
(Kagan,
PAGEOPH, 2007).
Bird, P., D. D. Jackson, Y. Y. Kagan,
C. Kreemer, and R. S. Stein, 2015.
GEAR1: a Global Earthquake
Activity Rate model constructed
from geodetic strain rates and
smoothed seismicity,
BSSA, accepted 2015/06/18
Fig. 1: Two parent forecasts at
threshold magnitude m5.767+:
(A) Seismicity parent forecast for
years 2005+. Mercator projection.
Logarithmic color‐ (or gray‐) scale
shows the rate density of
epicentroids corresponding to
shallow (≤70 km) hypocentroids, in
units of (km)^‐2 year^‐1.
(B) Tectonics parent forecast
for years 2005+. Conventions as in
part (A), and identical color scale.
Equal to model SHIFT-GSRM2f of
Bird and Kreemer (2015).
Preferred hybrid forecasts for
threshold magnitude m5.767+, both
with and without overlay of test
earthquakes:
(A) Preferred hybrid forecast H*
(log‐linear, with exponent d = 0.6 on
Seismicity) for years 2005+
compared to 1694 shallow test
earthquakes from GCMT catalog
years 2005‐2012. For test
earthquakes of m > 6, focal
mechanism is shown on lower focal
hemisphere.
(B) GEAR1 forecast (preferred
hybrid H*, updated to end‐2013) for
years 2014 and after. Mercator
projection. Logarithmic color scale
shows the rate density of
epicentroids corresponding to
shallow (≤70 km) hypocentroids, in
units of (km)^‐2 year^‐1.
Kagan & Jackson, GJI, 2000.
Focal mechanism forecast is calculated by summing
seismic moment tensors in 1000 km distance area and
evaluating eigenvectors of the sum tensor. We
compare this source forecast with other mechanisms to
measure degree of uncertainty (\Phi_1).
Focal mechanism forecast 2008-2012, based on 1977-2007
Earthquake forecast conclusions
• We present an earthquake forecast program
which quantitatively predicts both long- and
short-term earthquake probabilities.
• The program is numerically and rigorously
testable both retrospectively and prospectively as
done by CSEP worldwide, as well as in
California, Italy, Japan, New Zealand, etc.
• It is ready to be implemented as a technological
solution for earthquake hazard forecasting and
early warning.
END
Thank you
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