Supercycle in great earthquake recurrence along the Japan Trench over the last 4000 years
Usami et al. Geosci. Lett.
Supercycle in great earthquake recurrence along the Japan Trench over the last 4000 years
Kazuko Usami 0 3
Ken Ikehara 3
Toshiya Kanamatsu 2
Cecilia M. McHugh 1 4
0 Atmosphere and Ocean Research Institute, The University of Tokyo , 5-1-5, Kashiwanoha, Kashiwa-shi, Chiba 277-8564 , Japan
1 Earth and Environmental Sciences, Queens College, City University of New York , 65-30 Kissena Boulevard, Flushing, NY 11367 , USA
2 Research and Development Center for Earthquake and Tsunami, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) , 2-15 Natsushima-cho, Yokosuka 237-0061 , Japan
3 Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST) , Tsukuba Central 7, 1-1-1 Higashi, Tsukuba 305-8567 , Japan
4 Marine Geology and Geophysics, Lamont-Doherty Earth Observatory of Columbia University , PO Box 1000, Palisades, NY 10964 , USA
On the landward slope of the Japan Trench, the mid-slope terrace (MST) is located at a depth of 4000-6000 m. Two piston cores from the MST were analyzed to assess the applicability of the MST for turbidite paleoseismology and to find out reliable recurrence record of the great earthquakes along the Japan Trench. The cores have preserved records of ~ 12 seismo-turbidites (event deposits) during the last 4000 years. In the upper parts of the two cores, only the following earthquakes (magnitude M ~ 8 and larger) were clearly recorded: the 2011 Tohoku, the 1896 Sanriku, the 1454 Kyotoku, and the 869 Jogan earthquake. In the lower part of the cores, turbidites were deposited alternately in the northern and southern sites during the periods between concurrent depositional events occurring at intervals of 500-900 years. Considering the characteristics of the coring sites for their sensitivity to earthquake shaking, the concurrent depositional events likely correspond to a supercycle that follows giant (M ~ 9) earthquakes along the Japan Trench. Preliminary estimations of peak ground acceleration for the historical earthquakes recorded as the turbidites imply that each rupture length of the 1454 and 869 earthquakes was over 200 km. The earthquakes related to the supercycle have occurred over at least the last 4000 years, and the cycle seems to have become slightly shorter in recent years. Earthquakes off the Sanriku coast forming the alternative deposition of turbidites in the two cores have released a part of accumulated slip, as indicated by the turbidites deposited in only one core. Decreases in the release of accumulated slip have possibly caused the recent shortening of the supercycle.
Japan Trench; Earthquake; Turbidite; Supercycle
Background
The 2011 off the Pacific coast of Tohoku earthquake
(2011 Tohoku earthquake) occurred on March 11, 2011.
It was an interplate earthquake that occurred along the
Japan Trench with Mw 9.0
(Suzuki et al. 2011)
. This
earthquake triggered huge destructive tsunamis that hit
the Pacific coast of Northeast Japan, thus causing
extensive damage. This earthquake forced a revision of the
conventional understanding of the recurrence patterns of
great earthquakes along the Japan Trench
(Satake 2015)
.
These recurrence patterns have conventionally been
studied through historical and instrumental records on
the last few centuries. Therefore, the use of geological
records has become more important source of long
timescale evidence about the recurrence of great earthquakes.
Onshore tsunami deposits provide evidence that
significant earthquakes and tsunamis have impacted the Pacific
coast of Tohoku in the past
(Abe et al. 1990; Minoura
and Nakaya 1991; Minoura et al. 2001; Sawai et al. 2012,
2015; Ishimura and Miyauchi 2015; Takada et al. 2016;
Ishimura 2017)
. Even before the 2011 Tohoku
earthquake, two earthquakes along the Japan Trench (the A.D.
869 Jogan earthquake and the 1454 Kyotoku earthquake)
that generated giant tsunamis similar to the one in 2011
are indicated by historical records and tsunami deposits
(Satake et al. 2008; Namegaya and Yata 2014; Sawai et al.
2015)
. The 1896 Sanriku earthquake known as “tsunami
earthquake” also caused serious damage to the Tohoku
region
(Kanamori 1972; Tanioka and Satake 1996; Satake
et al. 2017)
and formed tsunami depo
sits (e.g., Takada
et al. 2016
). Although tsunamis that originated at great
distances have also produced some onshore deposits on
the Sanriku coast
(e.g., the 1960 Chilean tsunami
deposits; Kon’no et al. 1961)
, the major cause of large
tsunamis in this area is interplate earthquakes along the Japan
Trench
(Minoura and Nakaya 1991; Minoura et al. 2001;
Namegaya and Satake 2014; Sawai et al. 2015)
.
However, submarine landslides could also cause some large
tsunamis
(Tappin et al. 2001; Kawamura et al. 2014)
. In
general, it is difficult to discern the cause of a tsunami
solely on the basis of the characteristics of onshore
tsunami deposits. Seismo-turbidites (turbidites deposited by
earthquake-trig (...truncated)