Japan Trench Fast Drilling Project

Last updated

The Japan Trench Fast Drilling Project (JFAST) was a rapid-response scientific expedition that drilled oceanfloor boreholes through the fault-zone of the 2011 Tohoku earthquake. JFAST gathered important data about the rupture mechanism and physical properties of the fault that caused the huge earthquake and tsunami which devastated much of northeast Japan. [1] [2]

Contents

Background

The 2011 Tohoku-oki earthquake, with a moment magnitude of 9.0, was the largest in Japan's history, and severely damaged regions of northeast Honshu, with over 15,000 deaths and economic losses of $US 200 to 300 billion. [3] Because of the huge societal impact, there was an urgency among scientists to respond with information and research results to explain the disastrous event. Soon after the earthquake, researchers of the Integrated Ocean Drilling Program (IODP) began planning the Japan Trench Fast Drilling Project (JFAST) to investigate the earthquake with ocean floor boreholes to the plate boundary fault. [4] [5]

This ambitious project drilled boreholes through the fault that slipped during the earthquake in order to understand the unprecedented huge slip (40 to 60 meters) [6] that occurred on the shallow portion of the megathrust fault and was the primary source of the large tsunami that devastated much of the coast of northeast Honshu. There was much public interest in this high-profile scientific project with considerable Japanese [7] [8] and English [9] media coverage of the operations [4] [10] and results [1] [11] [12] [13]

Specific science objectives [14] included,

The site for the offshore drilling was located about 220 km east of Sendai in the region of very large fault slip during the earthquake near the Japan Trench.

Deep water drilling operations

The D/V Chikyu, operated by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) sailed on IODP Expedition 343 from the port of Shimizu, Shizuoka on April 1, 2012, within 13 months after the earthquake. Chikyu is the only research vessel with the capabilities for the necessary drilling in very deep water of over 6900 meters. Two months of operations from April 1 to 24 May 24, 2012 were scheduled for drilling several boreholes to carry out Logging while drilling (LWD), install temperature sensors and retrieve core samples. The extreme water depths caused many technical challenges that had to be considered, such as the strength of the long pipe string, onboard handling of the pipe sections, and instrument operations at very high water pressure. These aspects needed careful planning and new tools on the ship. Various equipment had not been previously used in such deep water and caused many problems and delays during the first month at sea. [14] Eventually difficult engineering problems were overcome enabling retrieval of borehole core and installation of a temperature observatory across the fault zone at a depth of about 820 meters below the sea floor. New records were set for scientific drilling including, longest drilling string (7740 m) from the ocean surface and deepest core from the ocean surface (7752 m). [10] [14]

Because of delays due to technical difficulties and bad weather, the temperature observatory could not be deployed during the main expedition. However, during the supplementary Expedition 343T from July 5 to 19 a new borehole was quickly drilled and the temperature sensors were installed [10]

Retrieval of the temperature data was scheduled for cruise KR13-04 during February 11 to 20, 2013 using the JAMSTEC ship R/V Kairei and Remotely Operated Vehicle (ROV) Kaiko-7000II. Kaiko-7000II is one of the few vehicles that can operate at 7000 meters water depth. Because of inclement weather and navigation problems the instruments could not be retrieved at this time. However, during the subsequent cruise KR13-08 from April 21 to May 9, 2013, the temperature instruments were successfully recovered on April 26.

Scientific results

Borehole stress

Fractures in the borehole wall (borehole breakouts) were used to estimate the stress field in the region close to the fault zone. These fractures can be observed in the wall resistivity records obtained from the LWD data. From the orientations and crack widths of the fractures, the direction and magnitude of the stress can be calculated. The results of these analyses show that the region has changed from a thrust fault regime before the earthquake to a normal fault regime after the earthquake. The horizontal stress became close to zero, indicating that almost all of the stress was released during the earthquake. [15] This confirms previous suggestions that the earthquake had a complete stress drop, which is different from most other large earthquakes.

Fault zone

From the core samples, geologic structure data and measurements of physical properties, a single plate-boundary fault zone was identified with a high level of confidence at a depth of about 820 meters below the seafloor. [16] The fault is localized in a thin layer of highly deformed pelagic clays. The entire section of the fault zone was not retrieved, but from the amount of the recovered and unrecovered sections, the total width of the fault zone is determined to be less than 5 meters. This is a considerably simpler and thinner plate-boundary fault than has been observed at other locations, [16] such as the Nankai Trough . The actual slip surface for the 2011 earthquake may not have been recovered, but it is assumed that the structures and physical properties of the core are representative of the entire fault zone.

Fault friction

One of the main objectives of JFAST was to estimate the level of friction on the fault during the earthquake. To determine the frictional strength, high-speed laboratory experiments were carried out on samples from the plate boundary fault zone. The measured shear stress strength for permeable and impermeable conditions yielded values of 1.32 and 0.22 MPa, respectively, with the equivalent values for the coefficient of friction of 0.19 and 0.03, respectively. [17] These results show that the fault slipped with very low levels of friction, which are lower than observed from other subduction zones, such as the Nankai Trough. The very low frictional strength for the material from the Japan Trench fault zone is much lower than typically observed for other types of rocks. The low friction properties are largely caused by the high content of the clay mineral smectite. [17] Examination of the microstructures in the laboratory samples, suggests that fluids are important in the faulting process and contribute to the low friction properties, possibly through thermal pressurization. [17]

The temperature measurements were also designed to estimate the frictional heat on the fault by measuring the thermal anomaly at the fault zone. A temperature signal was clearly observed in the data about 4 months after instrument installation which is 18 month after the earthquake. At that time the temperature in the fault zone was about 0.3 °C above the geothermal gradient. [18] This is interpreted to represent the frictional heat produced at the time of the earthquake. Analyses of these data showed that the coefficient of friction on the fault at the time of the earthquake was about 0.08 and the average shear stress on the fault was estimated to be 0.54 MPa. [18] The temperature measurements give independent and similar results to the laboratory friction experiments, and confirm the very low frictional properties of the fault. The low friction properties likely contributed to the very large slip during the earthquake.

Summary

JFAST is considered to be a successful rapid scientific response [1] to a natural hazard event that had a great societal impact. Technical challenges associated with drilling in very deep water of about 6900 meters [10] were overcome enabling borehole stress measurements, recovery of valuable core samples of the plate-boundary fault zone and collection of unique temperature measurements. The results of the scientific investigations show that the huge slip during the 2011 Tohoku earthquake occurred on a simple and thin fault zone composed of pelagic sediments with a high smectite content. [11] Both laboratory experiments on the fault zone material and temperature measurements across the fault zone, show that the friction level was very low during the earthquake. [11] The localized fault zone, low friction properties of its material and complete stress drop during the earthquake, are important characteristics that likely contributed to the huge slip during the earthquake.

See also

Related Research Articles

<span class="mw-page-title-main">Earthquake</span> Sudden movement of the Earths crust

An earthquake – also called a quake, tremor, or temblor – is the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they cannot be felt, to those violent enough to propel objects and people into the air, damage critical infrastructure, and wreak destruction across entire cities. The seismic activity of an area is the frequency, type, and size of earthquakes experienced over a particular time. The seismicity at a particular location in the Earth is the average rate of seismic energy release per unit volume.

<span class="mw-page-title-main">Japan Trench</span> Oceanic trench part of the Pacific Ring of Fire off northeast Japan

The Japan Trench is an oceanic trench part of the Pacific Ring of Fire off northeast Japan. It extends from the Kuril Islands to the northern end of the Izu Islands, and is 8,046 metres (26,398 ft) at its deepest. It links the Kuril–Kamchatka Trench to the north and the Izu–Ogasawara Trench to its south with a length of 800 kilometres (497 mi). This trench is created as the oceanic Pacific Plate subducts beneath the continental Okhotsk Plate. The subduction process causes bending of the down going plate, creating a deep trench. Continuing movement on the subduction zone associated with the Japan Trench is one of the main causes of tsunamis and earthquakes in northern Japan, including the megathrust Tōhoku earthquake and resulting tsunami that occurred on 11 March 2011. The rate of subduction associated with the Japan Trench has been recorded at about 7.9–9.2 centimetres (3.1–3.6 in)/yr.

<span class="mw-page-title-main">Cascadia subduction zone</span> Convergent plate boundary that stretches from northern Vancouver Island to Northern California

The Cascadia subduction zone is a 960 km (600 mi) fault at a convergent plate boundary, about 100–200 km (70–100 mi) off the Pacific coast, that stretches from northern Vancouver Island in Canada to Northern California in the United States. It is capable of producing 9.0+ magnitude earthquakes and tsunamis that could reach 30 m (98 ft). The Oregon Department of Emergency Management estimates shaking would last 5–7 minutes along the coast, with strength and intensity decreasing further from the epicenter. It is a very long, sloping subduction zone where the Explorer, Juan de Fuca, and Gorda plates move to the east and slide below the much larger mostly continental North American Plate. The zone varies in width and lies offshore beginning near Cape Mendocino, Northern California, passing through Oregon and Washington, and terminating at about Vancouver Island in British Columbia.

Megathrust earthquakes occur at convergent plate boundaries, where one tectonic plate is forced underneath another. The earthquakes are caused by slip along the thrust fault that forms the contact between the two plates. These interplate earthquakes are the planet's most powerful, with moment magnitudes (Mw) that can exceed 9.0. Since 1900, all earthquakes of magnitude 9.0 or greater have been megathrust earthquakes.

<span class="mw-page-title-main">Okhotsk microplate</span> Minor tectonic plate in Asia

The Okhotsk microplate is a proposed minor tectonic plate covering the Kamchatka Peninsula, Magadan Oblast, and Sakhalin Island of Russia; Hokkaido, Kantō and Tōhoku regions of Japan; the Sea of Okhotsk, as well as the disputed Kuril Islands.

The Integrated Ocean Drilling Program (IODP) was an international marine research program, running from 2003 to 2013. The program used heavy drilling equipment mounted aboard ships to monitor and sample sub-seafloor environments. With this research, the IODP documented environmental change, Earth processes and effects, the biosphere, solid earth cycles, and geodynamics.

<span class="mw-page-title-main">Seismicity of the Sanriku coast</span>

The seismicity of the Sanriku coast identifies and describes the seismic activity of an area of Japan. Seismicity refers to the frequency, type and size of earthquakes experienced over a period of time. The Sanriku Coast is a descriptive term referring to the coastal areas of the former provinces of Rikuō in Aomori, Rikuchū in Aomori, and Rikuzen in Miyagi.

Chikyū Japanese drill ship

Chikyū (ちきゅう) is a Japanese scientific drilling ship built for the Integrated Ocean Drilling Program (IODP). The vessel is designed to ultimately drill 7 km beneath the seabed, where the Earth's crust is much thinner, and into the Earth's mantle, deeper than any other hole drilled in the ocean thus far.

A slow earthquake is a discontinuous, earthquake-like event that releases energy over a period of hours to months, rather than the seconds to minutes characteristic of a typical earthquake. First detected using long term strain measurements, most slow earthquakes now appear to be accompanied by fluid flow and related tremor, which can be detected and approximately located using seismometer data filtered appropriately. That is, they are quiet compared to a regular earthquake, but not "silent" as described in the past.

<span class="mw-page-title-main">Nankai Trough</span> Trough off the coast of Japan

The Nankai Trough is a submarine trough located south of the Nankaidō region of Japan's island of Honshu, extending approximately 900 km (559 mi) offshore. 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.

<span class="mw-page-title-main">1994 offshore Sanriku earthquake</span> Earthquake in Japan

The 1994 offshore Sanriku earthquake occurred on December 28, 1994, at 12:19 UTC. This was a magnitude Mw 7.7 earthquake with epicenter located in the Pacific Ocean at about 180 km east of Hachinohe, Aomori. The intensity reached shindo 6 in Hachinohe, Aomori, about 187.6 km from epicenter. It could be felt in Tokyo, about 632.9 km from epicenter, with shindo 2. The Japanese Meteorological Agency put the magnitude at MJMA 7.5. Slip associated with this earthquake continued for more than a year and it has been termed an 'ultra-slow earthquake'.

<span class="mw-page-title-main">Hikurangi Margin</span> Subduction zone off the east coast of New Zealands North Island

The Hikurangi Margin is New Zealand's largest subduction zone and fault.

The International Ocean Discovery Program (IODP) is an international marine research collaboration dedicated to advancing scientific understanding of the Earth through drilling, coring, and monitoring the subseafloor. The research enabled by IODP samples and data improves scientific understanding of changing climate and ocean conditions, the origins of ancient life, risks posed by geohazards, and the structure and processes of Earth's tectonic plates and uppermost mantle. IODP began in 2013 and builds on the research of four previous scientific ocean drilling programs: Project Mohole, Deep Sea Drilling Project, Ocean Drilling Program, and Integrated Ocean Drilling Program. Together, these programs represent the longest running and most successful international Earth science collaboration.

Christie D. Rowe is a Professor of Geology at McGill University. She holds a Canada Research Chair in Earthquake Geology and was awarded the 2017 Geological Association of Canada W. W. Hutchison Medal.

<span class="mw-page-title-main">Emily Brodsky</span> Geophysicist

Emily E. Brodsky is a Professor of Earth Sciences at the University of California, Santa Cruz. She studies the fundamental physical properties of earthquakes, as well as the seismology of volcanoes and landslides. In 2023, she was elected to the National Academy of Sciences.

<span class="mw-page-title-main">Chelungpu Fault</span> Active seismic fault located in Taiwan

The Chelungpu Fault is an active fault located in Taiwan. It caused the 1999 Jiji earthquake.

<span class="mw-page-title-main">1993 Kushiro earthquake</span> Earthquake in Japan

The 1993 Kushiro–Oki earthquake was one of two large earthquake to strike the Japanese island of Hōkkaido within the same year. The earthquake with a magnitude of 7.6 Mw or 7.8 MJMA struck at 11:06 UTC or 08:06 pm JST on January 15 near the town of Ashoro. Shaking reached a maximum intensity of IX (Violent) on the Mercalli intensity scale, causing considerable damage, and was felt throughout the island, into northern Honshu, Sakhalin, and the Kuril Islands. As a result of the tremors, two people were killed and more than 600 were wounded.

The Nemuro-Oki earthquake in scientific literature, occurred on June 17 at 12:55 local time. It struck with an epicenter just off the Nemuro Peninsula in northern Hokkaidō, Japan. It measured 7.8–7.9 on the moment magnitude scale (Mw ), 8.1 on the tsunami magnitude scale (Mt ) and 7.4 on the Japan Meteorological Agency magnitude scale (MJMA ).

Toshihiko Shimamoto is a Japanese seismologist and professor of earthquake science at the Institute of Geology in Beijing and affiliated researcher at Kyoto University. His experimental research has contributed significantly to our understanding of earthquake mechanics.

Demian (Michael) Saffer is an American geophysicist based at The University of Texas at Austin where he is director of the University of Texas Institute for Geophysics and professor at the Department of Geological Sciences of the Jackson School of Geosciences. He studies the role of fluids and friction in the mechanics of subduction megathrust earthquakes.

References

  1. 1 2 3 Smithsonian.com Fault that Caused Japan's 2011 Earthquake is Thin and Slippery, Dec. 5, 2013
  2. ↑ Christian Science Monitor Japan's monster quake: Do scientists have key to decode future tremblors?, Dec. 6, 2013
  3. ↑ "Zhang, Top 5 Most Expensive Natural Disasters in History, AccuWeather.com, Mar. 30, 2011". Archived from the original on 2016-03-03. Retrieved 2014-11-06.
  4. 1 2 Nature News, http://www.nature.com/news/2011/111031/full/479016a.html Drilling ship to probe Japanese quake zone, Oct. 31, 2011
  5. ↑ phys.org, Chikyu to set sail for IODP expedition: Japan trench fast drilling project, March 9, 2012
  6. ↑ Fujiwara et al., The 2011 Tohoku-Oki earthquake: displacement reaching the trench axis, Science, 1240. doi: 10.1126/science.1211554, 2011
  7. ↑ Nippon Broadcasting System TV News, Japan, news story on Apr. 14, 2012
  8. ↑ Tokyo Broadcasting System Television News 23, featured story on May 3, 2012 (in Japanese)
  9. ↑ Discovery Channel Daily Planet (TV series) feature story on Mar. 9, 2012
  10. 1 2 3 4 phys.org, New subseafloor observatory begins measurement of frictional heating by the 2011 Tohoku, Japan earthquake, July 23, 2012.
  11. 1 2 3 livescience, Slippery Clay at Fault in 2011 Japan earthquake, Dec. 5, 2013
  12. ↑ redOrbit New Report Highlights Stress Change During 2011 Tohoku-Oki Earthquake, Feb. 8, 2013,
  13. ↑ liberty voice Slippery Clay Explains Mystery of Tohoku-Oki Earthquake and Tsunami, Dec. 6, 2013
  14. 1 2 3 Mori et al., Investigation of the Huge Tsunami from the 2011 Tōhoku-Oki, Japan, Earthquake Using Ocean Floor Boreholes to the Fault Zone, Oceanography 27, 132–137, 2014
  15. ↑ Lin et al., Stress state in the largest displacement area of the 2011 Tohoku-Oki earthquake, Science 339, 687-690, 2013
  16. 1 2 Chester et al., Structure and composition of the plate-boundary slip-zone for the 2011 Tohoku-oki earthquake Science 342, 1208-1211, 2013
  17. 1 2 3 Ujiie et al., Low coseismic shear stress on the Tohoku megathrust determined from laboratory experiments, Science 342, 1211-1214, 2013
  18. 1 2 Fulton et al., Low coseismic friction on the Tohoku-oki faulk determined from temperature measurements, Science 342, 1215-1217, 2013

Media coverage

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.