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Along-strike Variations in Shallow Earthquake Distribution and
Source Parameters along the Kurile-Kamchatka Arc
Susan L. Bilek (Earth and Environ. Science Dept., New Mexico Tech), Heather R. DeShon (CERI, University of Memphis),
E. Robert Engdahl (Dept. of Physics, Univ. of Colorado)
Observations in the last decade suggest a spectrum of slip durations for subduction zone earthquakes arising from rupture
velocities that range from typical ~3 km/s, to 1 km/s for tsunami earthquakes, and even slower for other slip events. In order
to understand conditions required to produce these slow rupture velocities, it is useful to clearly define areas where slow earthquakes
occur. Our project addresses this goal by a) determining source parameters for large catalogs of subduction zone earthquakes,
with an initial focus in expanding catalogs near documented tsunami earthquakes, and b) improving locations of these
earthquakes to define regions of the interface that produce slow slip events through a new methodology that improves on the
relocation technique of Engdahl, van der Hilst, and Buland (EHB). We show here results for 119 thrust mechanism earthquakes
near the plate interface in the Kurile-Kamchatka subduction zone, an area with 2 documented tsunami events in 1963 and 1975
and afterslip following large coseismic slip. We determine a variety of earthquake source parameters using IRIS waveform data
in multi-station body wave deconvolution methods and finite fault waveform inversion. Using the revised locations and their
moment-normalized source durations, we find patches of events with long rupture durations around the 1963 tsunami event,
along central Kuriles, and in southern Kamchatka, south of observed afterslip in 1997 (Figure 1).
References
Bilek, S.L., H.R. DeShon, and E.R. Engdahl, 2009, Along-Strike Variations in Shallow Earthquake Distribution and Source Parameters Along
the Kurile-Kamchatka Arc, EOS Trans AGU, 90(52), Fall Meet. Suppl., Abstract T23B-1908
Acknowledgements: We gratefully acknowledge NSF-OCE support for this project (OCE-0840908 to SLB, OCE-0841022 to HRD, and OCE-
0841040 to ERE.
Moment normalized rupture duration (NSD) for
earthquakes with revised locations along the Kurile-
Kamchatka subduction zone. Our results suggest more
recent earthquakes that occurred near the 1963 tsunami
earthquake (red star) and south of the 1997
afterslip (red rectangle) have long duration character,
suggesting the possibility of similar fault conditions
leading to both slip processes.
0 2 4 6 8 10
NSD (s)
1904
1923
1959
50˚
1952
2006
45˚
1958
1969
1963
1918
1952
40˚
145˚ 150˚ 155˚ 160˚
II-60 | 2010 IRIS Core Programs Proposal | Volume II | Earthquake Source Studies