Mechanism of subsidence of the Northeast Japan forearc during the late period of a gigantic earthquake cycle

Abstract

The forearc in Northeast Japan subsided (3–4 mm/year) in the interseismic ~100 years before the 2011 Tohoku earthquake (M W 9.1) just like it did during this event. This study attempts to understand the mechanism of the vertical displacement of the forearc during gigantic earthquake cycles via numerical modeling. The results suggest that the interseismic subsidence rate in the forearc increases with the duration of the locking of the asperity of the gigantic earthquake over several hundred years, due to the increasing slip deficit rate on the deeper parts of the plate interface. The increasing slip deficit rate is caused by both the decreasing the shear stress in the shear zone owing to the continuous locking of the asperity and the increasing the mobility of the continental lithosphere owing to the viscoelastic relaxation in the mantle wedge. The deep slip deficit rate extending to ~100 km depth of the plate interface is necessary to explain the observed interseismic forearc subsidence rate. The results also suggest hundreds of years of continuous locking of the asperities of a gigantic earthquake in the western Kuril subduction zone, where fast forearc subsidence has been observed as well.

Improving the Constraint on theMw7.1 2016 Off‐Fukushima Shallow Normal‐Faulting Earthquake With the High Azimuthal Coverage Tsunami Data From the S‐Net Wide and Dense Network: Implication for the Stress Regime in the Tohoku Overriding Plate

“…(2015a) showed that the normal‐faulting stress regime is dominant at depths shallower than ∼15 km in this region, while the reverse‐faulting stress regime is dominant at depths greater than ∼15 km, which is consistent with the hypothesis. We can also consider the topographic effects (Sasajima et al., 2019; Wang et al., 2019) for the formation of the horizontal extensional stress. There may be another possible interpretation for this contradiction that the stress regime switched to the reverse‐faulting regime again by the off‐Fukushima earthquake; However this is improbable because normal‐faulting seismicity can be found nearby, even after one year from the earthquake (Figure 1f).…”

Hourly-resolution Analysis of a Mussel Shell: Influence of Normal Tide and the Great Tsunami

“…The mussel bed was situated in the intertidal zone as estimated by the animal's common habitat 14,16 before the crustal movement caused by the 2011 Tohoku earthquake. Actual coseismic subsidence was not well documented in the region, but it may be approximately 100 cm, estimated in the forearc of Northeast Japan by a model calculation 26 . Correcting for subsidence after the tsunami, the specimens were probably located at 50-100 cm water depth on September 6 th , 2011.…”

Quantifying the inundation impacts of earthquake-induced surface elevation change by hydrological and hydraulic modeling

“…Both earthquake and flood are natural hazards which would cause devastating catastrophes. Land surface elevation changes caused by earthquake has been reported in some catchments 29 , 30 . In this study, we aim to quantify the flood hazard impacts of earthquake-induced surface elevation change.…”

“…Both natural and human activities can lead to land surface elevation changes, such as earthquake-induced tectonic movement 29 , 30 , sediment compaction 31 – 33 , coal mining 34 , sand mining 35 , and groundwater abstraction 36 , 37 . These temporal geomorphological processes were frequently occurred in coastal cities and caused significant impacts on flood hazards 38 – 41 .…”

“…The high-resolution digital elevation data are measured with Lidar by Kokusai Kogyo Corporation. Earthquake-induced land surface elevation data are available from the Geospatial Information Authority of Japan 29 , 30 . Land cover data are constructed from the Landsat-5 TM images 36 , 37 .…”