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"Sea of Japan"
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Effects of uncertainty in fault parameters on deterministic tsunami hazard assessment: examples for active faults along the eastern margin of the Sea of Japan
We investigated the effects of fault parameter uncertainty on the deterministic assessment of tsunami hazards for the submarine and coastal active faults in the Sea of Japan that were recently modeled by the Integrated Research Project on Seismic and Tsunami Hazards around the Sea of Japan. A key parameter in scenario-based tsunami assessment is the fault slip amount, which is usually calculated from empirical scaling relations that relate the fault size to the slip. We examined four methods to estimate the fault slip amounts and compared the coastal tsunami heights from the slip amounts obtained by two different empirical relations. The resultant coastal tsunami heights were strongly affected by the choice of scaling relation, particularly the fault aspect ratio (fault length/fault width). The geometric means of the coastal tsunami heights calculated from the two methods ranged from 0.69 to 4.30 with an average of 2.01. We also evaluated the effects of fault slip angles, which are also important parameters for controlling coastal tsunami heights, by changing the slip angles for faults in the southwestern and central parts of the Sea of Japan, where the strike-slip faults are concentrated. The effects of uncertainty of the fault slip angles (± 30° from the standard) on the coastal tsunami heights were revealed to be equal to or greater than those resulting from the choice of scaling relations; the geometric means of the coastal tsunami heights from the modified fault slip angles relative to the standard fault slip angles ranged from 0.23 to 5.88. Another important characteristic is that the locations of the maximum coastal tsunami height and the spatial pattern of the coastal tsunami heights can change with varying fault slip angles.
Journal Article
Change in the Recent Warming Trend of Sea Surface Temperature in the East Sea (Sea of Japan) over Decades (1982–2018)
Long-term trends of sea surface temperature (SST) of the East Sea (Sea of Japan, EJS) were estimated by using 37-year-long satellite data, for the observation period from 1982 to 2018. Overall, the SST tended to increase with time, for all analyzed regions. However, the warming trend was steeper in the earlier decades since the 1980s and slowed down during the recent two decades. Based on the analysis of the occurrence of events with extreme SST (high in the summertime and low in the wintertime), a shift toward the more frequent occurrence of events with extremely high SST and the less frequent occurrence of events with extremely low SST has been observed. This supports the observations of the consistent warming of the EJS. However, seasonal trends revealed continuous SST warming in the summertime, but frequent extreme SST cooling in the wintertime, in recent decades. The observed reduction in the warming rates occurred more frequently in specific regions of the EJS, where the occurrence frequency of events with extremely low SST was unusually high in the recent decade. The recent tendency toward the SST cooling was distinctively connected with variations in the Arctic Oscillation index. This suggests that changes in the Arctic Ocean environment likely affect the recently observed SST changes in the EJS, as one of the marginal seas in the mid-latitude region far from the polar region.
Journal Article
The other Australia/Japan living marine resources dispute : inferences on the merits of the southern bluefin tuna arbitration in light of the whaling case
In 2000, the case brought by Australia and New Zealand against Japan's unilateral experimental fishing programme for southern bluefin tuna controversially failed to reach the merits for lack of the arbitral tribunal's jurisdiction. It was widely supposed that it would ultimately have failed anyway because of international courts' reluctance to consider scientific matters, the dispute's underlying cause being the parties' scientific disagreements regarding both the tuna stock itself and the nature and risks of the experiment. In 2014, however, the ICJ decided in Australia's favour the case against Japan's scientific whaling, based on flaws in the design of that experiment. Reviewing the tuna experiment's evolving design, the propositions it was to (dis)prove and the use Japan intended for that proof, Andrew Serdy suggests that similar factors were at play in both disputes and that a similar outcome of the tuna case, though not inevitable, would have been amply justified -- Back cover.
Book
Reexamination of tsunami source models for the twentieth century earthquakes off Hokkaido and Tohoku along the eastern margin of the Sea of Japan
Large earthquakes around Japan occur not only in the Pacific Ocean but also in the Sea of Japan, and cause both damage from the earthquake itself and from the ensuing tsunami to the coastal areas. Recently, offshore active fault surveys were conducted in the Sea of Japan by the Integrated Research Project on Seismic and Tsunami Hazards around the Sea of Japan (JSPJ), and their fault models (length, width, strike, dip, and slip angles) have been obtained. We examined the causative faults of M7 or larger earthquakes in the Sea of Japan during the twentieth century, comprising events of 1940, 1964, 1983, and 1993, using seismic and tsunami data. The 1940 off Shakotan Peninsula earthquake (MJMA 7.5) appears to have been caused by the offshore active faults MS01, MS02, ST01, and ST02 as modeled by the JSPJ. The 1993 off the southwest coast of Hokkaido earthquake (MJMA 7.8) likely occurred on the offshore active faults OK03a, OK03b, and OK05, while the 1983 Central Sea of Japan earthquake (MJMA 7.7) probably related to MMS01, MMS04, and MGM01. For these earthquakes, the observed tsunami waveforms were basically reproduced by tsunami numerical simulation from the offshore active faults with the slip amounts obtained by the scaling relation with three stages between seismic moment and source area for inland earthquakes. However, the observed tsunami runup heights along the coast were not reproduced at certain locations, possibly because of the coarse bathymetry data used for the simulation. The 1983 west off Aomori (MJMA 7.1) and the 1964 off Oga Peninsula (MJMA 6.9) earthquakes showed multiple faults near the source area that could be used to reproduce the observed tsunami waveforms; therefore, we could not identify the causative faults. Further analysis using near-field seismic waveforms is required for their identification of their causative faults and their parameters. The scaling relation for inland earthquakes can be used to obtain the slip amounts for offshore active faults in the Sea of Japan and to estimate the coastal tsunami heights and inundation area which can be useful for disaster prevention and mitigation of future earthquakes and tsunamis.
Journal Article
Crust and uppermost mantle beneath the North China Craton, northeastern China, and the Sea of Japan from ambient noise tomography
A 3‐D shear velocity model of the crust and uppermost mantle to a depth of 100 km is presented beneath the North China Craton (NCC), northeastern China, the Korean Peninsula, and the Sea of Japan. Ambient noise Rayleigh wave tomography is applied to data from more than 300 broadband seismic stations from Chinese provincial networks (CEArray), the Japanese F‐Net, and the IRIS Global Seismic Network. Continuous data from 2007 to 2009 are used to produce group and phase velocity maps from 8 s to 45 s periods. The model is motivated to constrain the distributed intraplate volcanism, crustal extension, cratonic rejuvenation, and lithospheric thinning that are hypothesized for the study region. Numerous robust features are observed that impose new constraints on the geometry of these processes, but discussion concentrates only on four. (1) The North‐South Gravity Lineament follows the ∼40 km contour in crustal thickness, and crustal thickness is anticorrelated with water depth beneath the Sea of Japan, consistent with crustal isostasy for a crust with laterally variable composition. (2) The lithosphere is thin (∼70 km) beneath the Songliao‐Bohai Graben but seismically fast. (3) Even thinner more attenuated lithosphere bounds three sides of the eastern NCC (in a horseshoe shape), identifying a region of particularly intense tectonothermal modification where lithospheric rejuvenation may have reached nearly to the base of the crust. (4) Low‐velocity anomalies reach upward (in a Y shape) in the mantle beneath the eastern and western borders of the Sea of Japan, extending well into continental East Asia in the west, and are separated by a ∼60 km thick lithosphere beneath the central Sea of Japan. This anomaly may reflect relatively shallow slab dehydration in the east and in the west may reflect deeper dehydration and convective circulation in the mantle wedge overlying the stagnant slab. Key Points Obtaining unprecedented abundance of data for northeast Asia Identifying and removing disturbance signals from Kyushu microseism Getting 3D shear wave structures with high resolution and precision
Journal Article
Impact of local atmospheric circulation and sea surface temperature of the East Sea (Sea of Japan) on heat waves over the Korean Peninsula
South Korea has frequently suffered from heat waves, which are mainly attributable to anomalously prolonged high-pressure systems. There have been many studies regarding the role of large-scale circulation in the Korean Peninsula heatwaves, but the contribution of local-scale circulation and sea surface temperature has not been analyzed. This study investigates the impact of local circulation and sea surface temperature (SST) of the East Sea (Sea of Japan) on the surface temperature variations of the Korean Peninsula. Based on empirical orthogonal function (EOF) analysis of the detrended daily surface temperature anomalies from July to August, 1991–2020, high-temperature days were classified into three categories: high pressure (HP), easterly wind (EW), and both high pressure and easterly wind (HPEW). On EW days, the mean surface temperatures in the western part of the peninsula are 1.75 °C higher than those on the eastern part of the windward side, indicating foehn wind warming on the leeward side. Under the synergistic effects of foehn wind warming and high-pressure anomalies, the surface temperature is the highest on HPEW days. Regression analysis also shows that, when the SST of the East Sea increased by 1 °C, the surface temperatures in the western region on HPEW and EW days increased by 0.36 °C and 0.22 °C, respectively. In contrast, the SST effect in the western region is negligible on HP days owing to the lack of foehn wind warming. Sensitivity experiments using the high-resolution Weather Research and Forecasting (WRF) model also showed that foehn wind warming becomes stronger on EW and HPEW days with warmer East Sea SST. Our results suggest that local circulation and SST are important factors in high-temperature events in the Korean Peninsula.
Journal Article
Seismic velocity structure along the Sea of Japan with large events derived from seismic tomography for whole Japanese Islands including reflection survey data and NIED MOWLAS Hi-net and S-net data
We conducted seismic tomography for entire Japanese Islands including the Sea of Japan and the Pacific Ocean using arrival times from reflection survey as well as the routine seismic network. We successfully imaged the shallow zone along the Sea of Japan from offshore Yamagata to the Noto Peninsula by using air gun data. An extremely low-V shallow zone is imaged between Sado Island and Noto Peninsula. We also obtained detailed seismic velocity structure beneath the Pacific Ocean at depths of 20–50 km using S-net data. The 2007 Noto Peninsula, the 2007 offshore Chuetsu, and the 2019 offshore Yamagata earthquakes occurred at the boundary between high-Vp and low-Vp zones. The west side of the hypocenter of the 2019 offshore Yamagata earthquake at depths of 10–30 km has high-V corresponding to the Mogami Trough. This high-V zone passes through Awa Island and reaches Sado Basin between Sado Island and Honshu. A major rift zone in the Tohoku Arc extending from the Akita region to the Niigata region along the coast of Sea of Japan corresponds to high-V lower crust and a shallow Moho.
Journal Article
Spatiotemporal Seismicity Evolution and Seismic Hazard Potentials in the Western East Sea (Sea of Japan)
The earthquakes in the western East Sea (Sea of Japan) mostly occur in the continental margin off the east coast of the Korean Peninsula. The seismic hazard potentials in and around the western Ease Sea are studied based on analyses of tectonic structures, seismicity features, earthquake source properties, Coulomb stress changes, and strong ground motions. The earthquake source mechanisms suggest that paleo-rifting structures in the western East Sea were activated by the current stress field. A low stress cumulation rate results in the occurrence of earthquakes with long recurrence intervals. The background seismicity suggests that earthquakes with magnitudes Mw 5.0, 6.0, and 7.0 may occur within every ∼ 44, ∼ 336, and ∼ 2550 years at 95 % confidence level. The spatial distribution of earthquakes changes with time. Most earthquakes are clustered within ∼ 60 km from the coast. The seismicity analysis indicates an apparent increase of moderate-size (Mw 3–5) earthquakes since the 2011 Mw 9.0 Tohoku-Oki megathrust earthquake. Static stress changes by moderate-size inland earthquakes induce offshore events. The seismicity and Coulomb stress changes suggest high seismic potentials around the western margin of the Ulleung basin. Earthquakes with magnitudes Mw 6.0–7.0 in the western East Sea may produce peak ground accelerations of 0.2 g within the distance of ∼ 40–80 km, which includes the coastal regions.
Journal Article