In plate tectonics, the Nankai Trough marks a subduction zone that is caused by subduction of the Philippine Sea Plate beneath Japan, part of the Eurasian plate (Kanda et al., 2004). A biennial survey by Shizuoka Prefecture showed in 2017 that the percentage of residents “very interested” in the Nankai Trough or Tokai earthquakes stood … IODP Expedition 370 will seek to find the temperature limit of the deepest life on Earth by drilling in the Nankai Trough, where heat flow is particularly high near its boundary with the subducting young, hot Philippine Sea tectonic plate. Despite the uncertainty of when such an earthquake will occur, local authorities are already taking action to prepare … 1980 ). This plate boundary would be an oceanic trench except for a high flux of sediments that fills the trench. Katsushisa, K., Masayuki, T., 2004, Short-period seismic radiation zones of a megathrust fault along the Nankai, Trough deduced from inversion analysis of seismic intensity data, Journal of Seismilogical Society of Japan, v. 57, no. [5], The northeasternmost part of the megathrust, segment E, has not ruptured since 1854. All the dates shown in the table use the Gregorian calendar. The recent magnitude 7.3 earthquake on the southern island of Kyushu, which killed at least 49 people and destroyed thousands of homes, is a reminder that Japan remains exposed to frequent natural disasters. Seismically, the high bottom simulating reflectors are considered indicative of gas hydrates (Colwell et al., 2004). Plate-boundary earthquakes of magnitude 8 or greater along the Suruga–Nankai Trough subduction zone have repeated at intervals of 90–150 years, but with widely varying magnitudes and rupture areas. For those earthquakes that affect the Nankai region specifically, see, "Tectonic evolution of the Japanese island arc system", "The age and origin of the Pacific islands: a geological overview", "Splay fault and megathrust earthquake slip in the Nankai Trough", "Broad, weak regions of the Nankai Megathrust and implications for shallow coseismic slip", "Simulation of Earthquake Generation Process in a Complex System of Faults", "Probability of a great earthquake to recur in the Tokai district, Japan", "A Disaster Prevention and Earthquake Experience Guide", "Study: Damage from Nankai quake could hit 1,240 trillion yen", "A Disaster to Dwarf 3/11? But it’s always a good idea to be prepared for natural disasters when living in Japan, no matter where you are or how it smells on any given day. In 1999, the likelihood of the occurrence of a great earthquake in the Tokai area in the period 2000-2010 was estimated to be in the range of 0.35–0.45. It would cost as much as 40 per cent of Japan’s gross … Demets, C., Gordon, R., ARgus, D., Stein, S., 1994, Effects of recent revisions to the geomagnetic reversal time scale on estimates of current plate motions, Geophysical Research Letters, v. 21, n. 20 pp. The Nankai Trough (南海トラフ, Nankai Torafu, Southern Sea Trough) is a submarine trough located south of the Nankaidō region of Japan's island of Honshū, extending approximately 900 km (559 mi) offshore. The Predicted Nankai Quake", "Catalog of Damaging Earthquakes in the World (Through 2007)", https://en.wikipedia.org/w/index.php?title=Nankai_megathrust_earthquakes&oldid=987944741, Earthquake clusters, swarms, and sequences, Creative Commons Attribution-ShareAlike License, This page was last edited on 10 November 2020, at 04:25. is a submarine trough located south of Japan's island of Honshū, extending approximately 900 km offshore.In plate tectonics, the Nankai Trough marks a subduction zone that is caused by subduction of the Philippine Sea Plate beneath Japan, part of the Eurasian plate (Kanda et al., 2004). This has been attributed to post-depositional opal cementation that is preserving the porosity (Spinelli et al., 2007). In addition to informing earthquake disaster research, these findings also shed light on the marine sedimentary environment and plate tectonics of the Nankai Trough. 67–86. 391–404. At depth there is an increase in the smectite clay content in the sediments, inferring that there has been a change in the deposition source rock (Steurer et al., 2003). At its southwestern end, there is another triple junction, where the overriding plate becomes the Okinawa Plate. After the twenty-first century, the Global Navigation Satellite System-Acoustic ranging (GNSS-A) technique detected geodetic events such as co- and postseismic effects following the 2011 Tohoku-oki earthquake and slip-deficit rate distributions along the Nankai Trough subduction zone. There was also underground fluid flow with the fluids being much hotter than the present-day temperature of the sediments,[3] which affected mineralization and, potentially, the physical and biological properties of the region. Volti, T., Kaneda, Y., Zatsepin, S., Crampin, S., 2005, An anomalous spatial pattern of shear-wave spitting observed of Ocean Bottom Seismic data above a subducting seamount in the Nankai Trough, Geophysical Journal International, v. 163, pp. Nankai Trough Earthquake Information Along the Nankai Trough, megathrust earthquakes with a magnitude 8 or more occur repeatedly. Overview of Nankai Trough Mega Earthquake Operation Plan To be ready for a national crisis should the Nankai Trough Mega Earthquake occur, we are making every effort to promote various operations. The data in the news release came from a series of boreholes what were started in the late 1990s. The pattern of historical seismicity reveals that the megathrust surface is segmented, with five separate zones of rupturing identified, conventionally labelled A–E, from west to east. Hydrologic observatories were placed in boreholes drilled in 2000 (IODP sites 808 and 1173) in an attempt to quantify changes in pore-fluid pressure that are a result of the oncoming Philippine Sea plate (Davis et al., 2006). The presence of this 'weak' zone may lead to shallow coseismic rupture along the megasplay faults during megathrust earthquakes, explaining the large tsunamis created by these events.[4]. Tomaru, H., Lu, Z., Fehn, U., Muramatsu, Y., Matsumoto, R., 2007, Age variations of pore water iodine in the eastern Nankai Trough, Japan: Evidence for different methane sources in a large gas hydrate field, Geology, v. 35, no. A future great earthquake involving rupture along this and possibly other segments has been proposed as a major risk for the southern coast of Honshu. Had an unforgettable moment with one back in 2012 . Analysis of seismic reflection data suggests that some of the displacement is carried by a splay fault dipping at about 25°. These five subdivisions show interesting differences in earthquake behavior: frequency of earthquakes varying on a 90 to 150-year cycle (Mitsui, et al., 2004; Tanioka et al., 2004), similar slip occurrences along the fault segments, the order of subdivision faulting, and finally, different failure features. Sella, G., Dixon, T., Mao, A., 2002, REVEL: A model for Recent plate velocities from space geodesy, Journal of Geophysical Research, v. 107, n. B4. 11, pp. Muramatsu, Y., Doi, T., Tomaru, H., Fehn, U., Takeuchi, R., Matsumote, R., 2006, Hologen concentrations in pore waters and sediments of the Nankai, Trough, Japan: Implications for the origin of gas hydrates, Applied Geochemistry, v. 22, pp. For this reason, the government will issue "Nankai Trough Earthquake Temporary Information (Giant Earthquake Alert)" when an earthquake of magnitude 8 or more occurs due to a displacement of about half of the epicenter area, and a mechanism to call attention … [4] The area was originally a basin (Shikoku Basin) with active hydrothermal activity during its formation. On all but one occasion, rupture of segment C (±D ±E) has been followed by rupture of segments A+B within a few years. The age determination of the iodine indicated multiple methane sources. Shortly after the 2011 Tōhoku earthquake, new reports were released which indicated the … 367–382. More earthquake news on Strange Sounds and Steve Quayle. The fault is divided into five segments in three zones, which rupture separately or in combination, and depending on location, the resulting earthquakes are subdivided by zone from west to east into Nankai earthquakes, Tōnankai earthquakes, and Tōkai earthquakes. In this area, the main sedimentological controls for the accumulation of gas hydrates are the sand-rich areas of the trough (Collett, 2002). The Nankai Trough 南海トラフ (Nankai Torafu?) Gas hydrates nearest the trough appear to be sourced mainly from dewatering associated with subduction, while with increasing distance from the trough the sourcing is more a result of lateral movement of methane enriched waters (Muramatsu et al., 2006). [9] A death toll as high as 230,000 has been suggested for such an event.[10]. REVEL-based calculations indicate that there is no accumulation of strain at the trench. The detrital clays, primarily smectite, display variation over time and location in the Nankai Trough as well as the Shikoku basin. In order to minimize the damage from the Nankai Trough Earthquake, it is necessary to take countermeasures for liquefaction. Reaching temperatures of approximately 130 °C in other areas would require collecting cores from approximately 4 kilometers below the seafloor, rather than 1.2 kilometers as planned by Expedition 370. Krason, 1994, estimated that there are 0.42 to 4.2×1012 cubic meters of methane within the gas hydrates. Zhao, S., Wu, X., Hori, T., Smith, A., Kaneda, A., Takemoto, S., 2003, Deformation and stress localization at the Nankai subduction zone, southwest Japan, Earth and Planetary Science Letters, v. 206, pp. In 1999, the likelihood of the occurrence of a great earthquake in the Tokai area in the period 2000-2010 was estimated to be in the range of 0.35–0.45. The source of water for the formation of gas hydrates frequently comes from the dewatering of a subducting slab as well as the overriding plate (Muramatsu et al., 2006). The Nankai Trough is a 700-kilometer-long sea-bottom depression that runs about 100 km off the southern coast from Shizuoka Prefecture to the Shikoku region. 1300 years. Baba, T., Cummins, P. R., 2005, Contiguous rupture area of two Nankai Trough earthquakes revealed by high resolution tsunami waveform inversion. Well coring indicates the presence of at least three gas hydrate zones. IODP Expeditions drilled the accretionary complex of the Nankai Trough and reveal the thermal history with drill core analyses. Within the Nankai Trough there is a large amount of deformed trench sediments (Ike, 2004), making one of Earth's best examples of accretionary prism. 73–84. [1] The earthquake measured between 8.1 and 8.4 on the moment magnitude scale , … Takahashi, N., Kodaira, S., Park, J., Deibold, J., 2003, Heterogeneous structure of western Nankai seismogenic zone deduced by multichannel reflection data and wide-angle seismic data. The northern part of the trough is known as the Suruga Trough, while to the east is the Sagami Trough. Using recent ocean bottom seismograph studies, it has been determined that most of the seismicity occurs near the trough axis (Obana et al., 2006). Although Nankai Trough Earthquakes occurred with a roughly 100 - 150 year cycle, they have various repetition intervals and source regions. Kastner, 2001, Gas ydrates in convergent margins: formation, occurrence, geochemistry, and global significance. On the other hand, M w 7-class earthquakes have repeatedly occurred in the Hyuga-nada Sea off Kyushu, southwest Japan, at a time interval of 10–20 years (e.g., Shiono et al. The information concerning the gas hydrates in the Nankai Trough was initially published in 2000 by the Japan National Oil Corporations. Conventional geologic estimates of plate movement velocities are difficult in the Nankai Trough because there are no spreading ridges that bound the tectonic plate. The conversion of smectite to illite (illitization) in subduction zones is likely driven by the higher temperature found in the subduction zone as opposed to non-subducting sediments (Saffer et al., 2005). Other interesting results of the pressure measurements were the pressure changes that resulted from sediment deformation near boreholes and the effect of very low earthquake swarms at the time of pressure changes (Davis et al., 2006). Tanioka, Y., Kusunose, T., Babu, T., Haseqawa, Y., 2004, Large earthquake along the Nankai trough, the 1944 Tanankai earthquake (Mw 8.0) and two 2004 Tonankai-oki earthquakes (Mw 7.2 and 7.4). [1] Its thermal history is complex due to multiple heating events or property changes. Recently there has been an increase in interest in the release of water from illite clays in subducting sediments. Site 808 is located in the front section of the main thrust fault, while site 1173 is located approximately 11 km from the frontal thrust zone (Hitoshi et al., 2006). Some sources use the Julian calendar for the earlier earthquakes in the list. However, using the Eurasia to North America plate motion, the estimated rate was 2–4 mm/yr (DeMets et al., 1990). 215–226. The underlying fault, the Nankai megathrust, is the source of the devastating Nankai megathrust earthquakes, while the trough itself is potentially a major source of hydrocarbon fuel, in the form of methane clathrate. 124. The area remains seismically active, and future earthquakes are anticipated, with a high risk of a Nankai earthquake in the near future, which could be potentially very damaging. Is no accumulation of strain at the trench a lot of earthquakes, considering the time lapse 70. The Nankai Trough runs roughly parallel to the east is the Nankai Trough is known as the Shikoku )... 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