Quake may hit trench, says expert
Less than 100km off the coast of Hawke's Bay is a deep-water trench that could be the site of a potential megathrust earthquake similar to the 2011 Japan earthquake, says seismologist Kevin Furlong.
Although we understand the general concept and general physics of megathrusts - the big subduction zone earthquakes - we are finding in our data from recent major events such as in Sumatra [Boxing Day 2004], Chile in 2010, and most recently in Japan, that they each have characteristics that differ from each other, and our existing models of how we might think they should behave during the actual earthquake rupture are incomplete," he said.
"Most of the time, as was the case in Japan for the past several hundred years at least, segments rupture individually and so maximum earthquakes are in the mid-to high magnitude 7 range. But on rare occasions, such as in 2011 in Japan, bigger ruptures can occur.
"We need to decide how best to manage that potential and uncertainty."
The trench will soon be part of a global study into megathrust earthquakes.
Scientists are warning of the possibility of a megathrust earthquake near New Zealand.
Practical Guide to Earthquakes - 34/72
Although Japan is the geologically most studied country in the world, the size of the 2011 M9.0 earthquake was a surprise. One of the reasons for this is that forecasts of future earthquakes were based on the history of past earthquakes.
Secend If you find two most dangerous months in every year for M 8.2 + I will be very happy to see that, also I already post some possible areas in this thread for M 8.2 + but need more time to see where will probably hit ..
Earthquake scientists started to rewrite their predictive models.
Abstract: An unusually large tsunami was generated by the AD 869 Jogan earthquake, off Miyagi prefecture along the Japan Trench. The tsunami brought deposits on the Ishinomaki and Sendai plains, both in Miyagi prefecture, and Ukedo river-mouth lowland of Namie Town, Fukushima prefecture. Horizontal distance between the most inland tsunami deposit and the estimated past coastline is about 3 km in Ishinomaki plain, 3-4 km in Sendai plain, and 1.5 km in Ukedo area. We computed tsunami inundation at these locations from two fault models of interplate earthquakes: one is a 100 km long fault with 10 m slip (Mw=8.3) and the other is a 200 km long fault with 7 m slip (Mw=8.4). We also examined four other fault models with variable fault depths and locations. In the simulation, artificial structures such as breakwaters and reclaimed lands were removed from the present topography, and the coastlines were modified to reproduce the topography at the time of the Jogan earthquake. Comparison of the computed inundation areas with the distribution of tsunami deposits indicate that the source of a 200 km long fault with 7 m slip can reproduce the distribution of the tsunami deposits in both plains and Ukedo river-mouth lowland.
Just days before the Great East Japan Earthquake, a government panel softened the wording of a report warning that a massive tsunami could strike northeastern Japan after three utilities with nuclear power plants begged it to do so, it has been learned.
According to interviews and documents made available Saturday, staff from Tokyo Electric Power Co., Tohoku Electric Power Co. and Japan Atomic Power Co. asked the secretariat of the Earthquake Research Committee to alter the draft of the report at a meeting on March 3, 2011.
The report suggested a massive tsunami similar to the one triggered by the Jogan Earthquake in 869 could be spawned off Miyagi and Fukushima prefectures, they said. The Jogan quake had an estimated magnitude of 8.3 and killed about 1,000 people.
A final version of the report has yet to be released in light of the earthquake and tsunami that actually hit the region eight days later, but some members of the committee called the revelation “unbelievable.”
The three utilities asked the secretariat in the Education, Culture, Sports, Science and Technology Ministry to change the wording to avoid giving people the “misunderstanding” that massive quakes similar to the Jogan quake actually occurred in the past.
In reply, the secretariat told the three utilities, “We’re not changing the context but we’re going to do something so it may not induce such misunderstanding.”
A few days later the ministry revised the draft. The reworded version said “further study” is required to decide if massive quakes similar to the Jogan quake took place because “appropriate data are insufficient.”
Volume 290, Issues 1–4, 1 December 2011, Pages 46–50
New insights of tsunami hazard from the 2011 Tohoku-oki event
Kazuhisa Goto a, b,
Catherine Chagué-Goff c, d,
Shigehiro Fujino e,
James Goff c,
Bruce Jaffe f,
Yuichi Nishimura g,
Bruce Richmond f,
Daisuke Sugawara b,
Witold Szczuciński h,
David R. Tappin i,
Robert C. Witter j,
Eko Yulianto k
a Planetary Exploration Research Center, Chiba Institute of Technology, Tsudanuma, Chiba 275-0016, Japan
b Disaster Control Research Center, Tohoku University, Sendai, Miyagi, 980-8579, Japan
c Australia-Pacific Tsunami Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia
d Australian Nuclear Science and Technology Organisation, Kirrawee DC, NSW 2232, Australia
e University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan
f US Geological Survey, Santa Cruz, CA, 95060, United States
g Hokkaido University, Sapporo, Hokkaido 060-0810, Japan
h Institute of Geology, A. Mickiewicz University, Poznań 61-606, Poland
i British Geological Survey, Nottingham, United Kingdom
j Oregon Department of Geology and Mineral Industries, OR, 97365, United States
k Indonesian Institute of Science, Jakarta, Indonesia
We report initial results from our recent field survey documenting the inundation and resultant deposits of the 2011 Tohoku-oki tsunami from Sendai Plain, Japan. The tsunami inundated up to 4.5 km inland but the > 0.5 cm-thick sand deposit extended only 2.8 km (62% of the inundation distance). The deposit however continued as a mud layer to the inundation limit. The mud deposit contained high concentrations of water-leachable chloride and we conclude that geochemical markers and microfossil data may prove to be useful in identifying the maximum inundation limit of paleotsunamis that could extend well beyond any preserved sand layer. Our newly acquired data on the 2011 event suggest that previous estimates of paleotsunamis (e.g. 869 AD Jōgan earthquake and tsunami) in this area have probably been underestimated. If the 2011 and 869 AD events are indeed comparable, the risk from these natural hazards in Japan is much greater than previously recognized.
► The first results of a geological survey following the 2011 Tohoku-oki tsunami. ► The tsunami inundated and left sediment deposits up to 4.5 km inland. ► 62% of the inundation distance was covered with sand. ► The 869 AD Jōgan earthquake and tsunami have probably been underestimated.
NOAA Significant Earthquake Database - 8.6 Ms
Date-Time Tuesday, February 05, 2013 at 10:24:41 UTC Tuesday, February 05, 2013 at 02:24:41 AM at epicenter Time of Earthquake in other Time Zones
Location 38.006°N, 115.455°W
Depth 21.5 km (13.4 miles) Region NEVADA
Distances 42 km (26 miles) NNE (22°) from Tempiute, NV 50 km (31 miles) NNW (336°) from Hiko, NV 50 km (31 miles) SSW (212°) from Hot Creek, NV 93 km (58 miles) WNW (298°) from Caliente, NV 203 km (126 miles) N (354°) from Las Vegas, NV
Location Uncertainty horizontal +/- 1 km (0.6 miles); depth +/- 0.5 km (0.3 miles)
Parameters NST= 38, Nph= 27, Dmin=74 km, Rmss=0.2 sec, Gp=122°, M-type=local magnitude (ML), Version=9
Source Seismological Laboratory, University of Nevada, Reno Event ID nn00401855