Progress and remaining problems in subduction paleoseismology along the Pacific coast of northeast Japan

2021 ◽  
Author(s):  
Yuki Sawai
Keyword(s):  
Numerical Simulations ◽  
Earth Science ◽  
Plate Boundary ◽  
Historical Record ◽  
Japan Trench ◽  
Tsunami Deposit ◽  
Kuril Trench ◽  
Rupture Area ◽  
2011 Tohoku Tsunami ◽  
The Pacific

<p>In the last two decades, tsunami geology in northeast Japan (Hokkaido and Tohoku) has focused on extending the record of tsunamis beyond the range of historical documents in the region. In Hokkaido facing to southern Kuril trench, recurrent sandy deposits interbedded with peat are regarded as evidence of historical and prehistoric tsunamis. Distribution of one of the sand layers just below a historic tephra (Ko-c2; 1694 CE), so-called 17th-century tsunami deposit, exceeds historical and recent tsunami inundations in eastern Hokkaido. Numerical simulations to reproduce the distributions first suggested a multi-segment fault model with unimodal slip (Mw > 8.4; Nanayama et al., 2003 in Nature), and later with variable slip (Mw > 8.8; Ioki and Tanioka, 2016 in EPSL). Tohoku region, facing to Japan trench, has longer historical record than Hokkaido and the oldest historical earthquake is the Jogan event in 869 CE. Numerical simulations constrained by spatial distributions of the tsunami deposits, coastal submergence, and observation of the 2011 Tohoku tsunami deposit suggest that the 869 event was a plate-boundary rupture at least 200 km long along the Japan Trench (Mw > 8.3–8.6). After the 2011 Tohoku event, a large tsunami in 1454 CE (Kyotoku event) became reexamined and considered to have been generated by a rupture area including the Miyagi-oki region (part of the Jogan rupture). If the 869. 1454, and 2011 events were similar, recurrence of earthquakes in Japan trench is more periodic than southern Kuril trench.   This presentation is based on descriptions and discussion in Sawai (2020) in Earth Science Reviews.  </p>

scholarly journals Three Thousand Year Paleotsunami History of Southern Part of Japan Trench

2020 ◽  
Author(s):  
Hokuto Higaki ◽  
Kazuhisa Goto ◽  
Hideaki Yanagisawa ◽  
Daisuke Sugawara ◽  
Takashi Ishizawa
Keyword(s):  
Low Frequency ◽  
Large Earthquake ◽  
High Elevation ◽  
Japan Trench ◽  
Tsunami Deposit ◽  
Geological Evidence ◽  
Chiba Prefecture ◽  
Rupture Area ◽  
Grain Size Distributions ◽  
History Of

Abstract Paleotsunami studies along the southern part of Japan Trench are scarce. Additional geological evidence must be collected. This study conducted field survey and multi-proxy analysis for drilling cores taken from a pond of Choshi City, Chiba prefecture, Japan, where the 1677 Enpo tsunami deposit was reported earlier. The pond is suitable for detection of sedimentary evidence of low-frequency but large tsunamis only because it is located at a high elevation (11 m). Three event deposits are intercalated in the three thousand year long continuous mud and peat sequences. Based on multi-proxy analyses conducted of grain size distributions, diatom assemblages, and geochemical markers, these event deposits were identified as tsunami deposits; the most recent was the AD 1677 Enpo tsunami. The estimated recurrence interval of the tsunami is approximately 700 years, which is comparable to those of the central part of the Japan Trench. It is noteworthy that the timing of these tsunami events along the southern part of the Japan Trench seems to have been close (few tens of years intervals) before or after the occurrence of large earthquakes and tsunamis along the central part of the Japan Trench. Therefore, a spatial-temporal relation of earthquake and tsunami generations might exist between central and southern parts of the Japan Trench, which might be explained by drastic changes of stress fields surrounding the rupture area of a huge earthquake. Considering the current situation, by which the Mw=9.0 2011 Tohoku-oki earthquake had occurred at central part of the Japan Trench, this possibility should be investigated carefully from perspectives of seismology and history because risks of future occurrence of large earthquake and tsunami events along the southern part of Japan Trench might be extremely high.

scholarly journals A new probabilistic seismic hazard assessment for greater Tokyo

2006 ◽  
Vol 364 (1845) ◽  
pp. 1965-1988 ◽  
Author(s):  
Ross S Stein ◽  
Shinji Toda ◽  
Tom Parsons ◽  
Elliot Grunewald
Keyword(s):  
Active Faults ◽  
Plate Boundary ◽  
Seismic Hazard Assessment ◽  
Historical Record ◽  
Probabilistic Seismic Hazard Assessment ◽  
Earthquake Hazards ◽  
Seismic Behaviour ◽  
Ground Acceleration ◽  
The Past ◽  
The Pacific

Tokyo and its outlying cities are home to one-quarter of Japan's 127 million people. Highly destructive earthquakes struck the capital in 1703, 1855 and 1923, the last of which took 105 000 lives. Fuelled by greater Tokyo's rich seismological record, but challenged by its magnificent complexity, our joint Japanese–US group carried out a new study of the capital's earthquake hazards. We used the prehistoric record of great earthquakes preserved by uplifted marine terraces and tsunami deposits (17 M ∼8 shocks in the past 7000 years), a newly digitized dataset of historical shaking (10 000 observations in the past 400 years), the dense modern seismic network (300 000 earthquakes in the past 30 years), and Japan's GeoNet array (150 GPS vectors in the past 10 years) to reinterpret the tectonic structure, identify active faults and their slip rates and estimate their earthquake frequency. We propose that a dislodged fragment of the Pacific plate is jammed between the Pacific, Philippine Sea and Eurasian plates beneath the Kanto plain on which Tokyo sits. We suggest that the Kanto fragment controls much of Tokyo's seismic behaviour for large earthquakes, including the damaging 1855 M ∼7.3 Ansei-Edo shock. On the basis of the frequency of earthquakes beneath greater Tokyo, events with magnitude and location similar to the M ∼7.3 Ansei-Edo event have a ca 20% likelihood in an average 30 year period. In contrast, our renewal (time-dependent) probability for the great M ≥7.9 plate boundary shocks such as struck in 1923 and 1703 is 0.5% for the next 30 years, with a time-averaged 30 year probability of ca 10%. The resulting net likelihood for severe shaking ( ca 0.9 g peak ground acceleration (PGA)) in Tokyo, Kawasaki and Yokohama for the next 30 years is ca 30%. The long historical record in Kanto also affords a rare opportunity to calculate the probability of shaking in an alternative manner exclusively from intensity observations. This approach permits robust estimates for the spatial distribution of expected shaking, even for sites with few observations. The resulting probability of severe shaking is ca 35% in Tokyo, Kawasaki and Yokohama and ca 10% in Chiba for an average 30 year period, in good agreement with our independent estimate, and thus bolstering our view that Tokyo's hazard looms large. Given $1 trillion estimates for the cost of an M ∼7.3 shock beneath Tokyo, our probability implies a $13 billion annual probable loss.

scholarly journals Structure and lithology of the Japan Trench subduction plate boundary fault

Tectonics ◽  
2015 ◽  
Vol 34 (1) ◽  
pp. 53-69 ◽  
Author(s):  
James D. Kirkpatrick ◽  
Christie D. Rowe ◽  
Kohtaro Ujiie ◽  
J. Casey Moore ◽  
Christine Regalla ◽  
...  
Keyword(s):  
Plate Boundary ◽  
Japan Trench ◽  
Boundary Fault

scholarly journals On the enigmatic birth of the Pacific Plate within the Panthalassa Ocean

2016 ◽  
Vol 2 (7) ◽  
pp. e1600022 ◽  
Author(s):  
Lydian M. Boschman ◽  
Douwe J. J. van Hinsbergen
Keyword(s):  
Triple Junction ◽  
Tectonic Evolution ◽  
Plate Boundary ◽  
Pacific Plate ◽  
Plate Tectonic ◽  
Point Location ◽  
Marine Magnetic Anomalies ◽  
The Pacific ◽  
History Of ◽  
Ridge System

The oceanic Pacific Plate started forming in Early Jurassic time within the vast Panthalassa Ocean that surrounded the supercontinent Pangea, and contains the oldest lithosphere that can directly constrain the geodynamic history of the circum-Pangean Earth. We show that the geometry of the oldest marine magnetic anomalies of the Pacific Plate attests to a unique plate kinematic event that sparked the plate’s birth at virtually a point location, surrounded by the Izanagi, Farallon, and Phoenix Plates. We reconstruct the unstable triple junction that caused the plate reorganization, which led to the birth of the Pacific Plate, and present a model of the plate tectonic configuration that preconditioned this event. We show that a stable but migrating triple junction involving the gradual cessation of intraoceanic Panthalassa subduction culminated in the formation of an unstable transform-transform-transform triple junction. The consequent plate boundary reorganization resulted in the formation of a stable triangular three-ridge system from which the nascent Pacific Plate expanded. We link the birth of the Pacific Plate to the regional termination of intra-Panthalassa subduction. Remnants thereof have been identified in the deep lower mantle of which the locations may provide paleolongitudinal control on the absolute location of the early Pacific Plate. Our results constitute an essential step in unraveling the plate tectonic evolution of “Thalassa Incognita” that comprises the comprehensive Panthalassa Ocean surrounding Pangea.

scholarly journals Distribution of the Pacific/North America motion in the Queen Charlotte Islands-S. Alaska plate boundary zone

2003 ◽  
Vol 30 (14) ◽  
Author(s):  
Stéphane Mazzotti ◽  
Roy D. Hyndman ◽  
Paul Flück ◽  
Alex J. Smith ◽  
Michael Schmidt
Keyword(s):  
North America ◽  
Plate Boundary ◽  
Boundary Zone ◽  
Queen Charlotte Islands ◽  
The Pacific ◽  
Plate Boundary Zone

scholarly journals LINEARIZATION OF RELATIVE HUMIDITY OVER THE PACIFIC OCEAN ON THE EQUATORIAL LINE

2019 ◽  
Vol 16 (33) ◽  
pp. 630-640
Author(s):  
C. M. DÍEZ ◽  
C. J. SOLANO
Keyword(s):  
Pacific Ocean ◽  
Relative Humidity ◽  
Earth Science ◽  
Southern Oscillation ◽  
Correlation Coefficients ◽  
East Side ◽  
The West ◽  
Enso Events ◽  
The Pacific ◽  
The Pacific Ocean

The atmosphere system is ruled by the interaction of many meteorological parameters, causing a dependency between them, i.e., moisture and temperature, both suitable in front of any anomaly, such as storms, hurricanes, El Niño-Southern Oscillation (ENSO) events. So, understanding perturbations of the variation of moistness along the time may provide an indicator of any oceanographic phenomenon. Annual relative humidity data around the Equatorial line of the Pacific Ocean were processed and analyzed to comprehend the time evolution of each dataset, appreciate anomalies, trends, histograms, and propose a way to predict anomalous episodes such ENSO events, observing abnormality of lag correlation coefficients between every pair of buoys. Datasets were taken from the Tropical Atmosphere Ocean / Triangle Trans-Ocean Network (TAO/TRITON) project, array directed by Pacific Environmental Laboratory (PMEL) of the National Oceanic and Atmospheric Administration (NOAA), and the Japan Agency for Marine-Earth Science and Technology (JAMSTEC). All the datasets were processed, and the code was elaborated by the author or adapted from Mathworks Inc. Even occurrences of relative humidity in the east side of the Pacific Ocean seem to oscillate harmonically, while occurrences in the west side, do not, because of the size of their amplitudes of oscillations. This fact can be seen in the histograms that show Peak shapes in the east side of the ocean, and Gaussians in the west; lag correlation functions show that no one pair of buoys synchronize fluctuations, but western buoys are affected in front of ENSO events, especially between 1997-98. Definitely, lag correlations in western buoys are determined to detect ENSO events.

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