Supercycle in great earthquake recurrence along the Japan Trench over the last 4000 years

Abstract

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.

Event Stratigraphy in a Hadal Oceanic Trench: The Japan Trench as Sedimentary Archive Recording Recurrent Giant Subduction Zone Earthquakes and Their Role in Organic Carbon Export to the Deep Sea

“…Ikehara et al (2016Ikehara et al ( , 2018 and Bao et al (2018) reported thick event deposits from sediment cores along the central Japan Trench that are linked to the AD 2011 Tohoku-oki, AD 1454 Kyotoku, and AD 869 Jogan earthquakes. Similarly large earthquakes older than these events have also been documented from widespread tsunami deposits (Satake, 2015) and marine sediments on the mid-slope terrace (Usami et al, 2018).…”

“…Remarkably, the 2011 earthquake delivered >1 Tg (10 12 g) of OC to the Japan Trench between 36.0 • and 39.5 • N through the resedimentation of spatially widespread remobilization of surficial sediment with a total volume of ∼0.2 km 3 (Kioka et al, 2019). Moreover, several cores from the central part of the Japan Trench document evidence for event deposits related to surficial sediment remobilization triggered by older large earthquakes in the last few thousands of years, including the well-known AD 1454 Kyotoku and AD 869 Jogan earthquakes (Ikehara et al, 2016(Ikehara et al, , 2018Usami et al, 2018). Yet, little is understood about (1) the temporal and spatial extent of the earthquake-triggered event deposits along the plate subduction zone, (2) whether older deposits may indicate prehistoric large earthquakes, and (3) the importance of recurrent large earthquakes for the carbon cycle at subduction margins.…”

Surface rupture and characteristics of a fault associated with the 2011 and 2016 earthquakes in the southern Abukuma Mountains, northeastern Japan, triggered by the Tohoku-Oki earthquake

“…Paleoseismic studies estimated recurrence intervals (based on the most recent and penultimate surface rupturing events) of 800-5900 years for the Yunodake fault (Miyashita 2018) and > 12,000 years for the Itozawa fault (Toda and Tsutsumi 2013;Niwa et al 2013). These are much longer than the recurrence interval of 500-700 years for the megathrust earthquake supercycle along the Japan Trench (e.g., Satake and Fujii 2014;Satake 2015;Sawai et al 2015;Usami et al 2018). No historical destructive inland earthquakes had been recorded before the 2011 Iwaki earthquake in the southern Abukuma Mountains (Usami 2013).…”

“…The paleoseismic histories of normal faults in the southern Abukuma Mountains that were triggered by the Tohoku-Oki earthquake are an important aspect of the interaction between megathrust earthquakes and inland stress changes. Published examples include the evidence of inland triggered earthquakes associated with the AD 1454 Kyotoku (M w > 8.4; Sawai et al 2015) and AD 869 Jogan earthquakes (M w > 8.6; Namegaya and Satake 2014), considered the two most recent megathrust events before the 2011 Tohoku-Oki earthquake (e.g., Satake and Fujii 2014;Satake 2015;Usami et al 2018). In the case of the 2011 Iwaki earthquake, which ruptured both the Yunodake and Itozawa faults, Miyashita (2018) reported that the Yunodake fault ruptured in 5900-6700 cal BP and 800-6200 cal BP and suggested that the later event could have been synchronous with the AD 869 Jogan earthquake.…”

“…10 Correlation of events on the Mochiyama fault and paleoearthquakes on the Yunodake and Itozawa faults. The bottom plot shows the timing of paleomegathrust earthquakes based on turbidite paleoseismology in the Japan Trench (Usami et al 2018) events is 0.98, or a probability of ~ 35% that these events were synchronous. If they occurred in 800-1310 cal BP, they could correspond to the AD 869 Jogan megathrust earthquake, but not the AD 1454 Kyotoku earthquake or the T4-1 earthquake of ~ 1500 cal BP (unknown magnitude; Fig.…”