Category Archives: Japan

Today in Geological History; June 3rd – The 25th Anniversary of Unzen

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Today marks the 25th anniversary of the pyroclastic flow from Mount Unzen which claimed the lives of 43 people.

Mount Unzen

Mount Unzen is actually several over lapping volcanoes on Japan’s island of Kyushu. It was the cause of Japan’s largest ever volcanic disaster in 1792 when a lava domed collapsed and caused a mega tsunami which killed nearly 15,000 people. After this even the volcano lay silent until beginning to stir in 1989.

Seismic swarms began in the November of 89 about 10 km west of the summit and gradually migrated eastward until the first phreatic eruption a full year later in November 1990. By May 20th 1991 fresh lava began to flow from the highly inflated summit area prompting the evacuation of almost 12,000 locals.

volcano-unzenThe threat of another eruption to the scale of 1792 brought journalists and scientists alike flocking to the surrounding area to monitor the activity of Unzen and its potential threat. Sadly this curiosity resulted in the deaths of 43 when on June 3rd activity peaked due to a possible lava dome collapse. This sent a huge pyroclastic flow surging down its flanks and funnelled in to a valley point in the direction where volcanologists and journalists had set up a base at what was thought to be a safe distance, over 4.5 km, from the summit.

Activity continued well in to 1995 and over 10,000 pyroclastic flows were recorded over this period. By the end of the eruption a new lava dome was in place 1.2 by 8 km wide. Its volume was approximated at 0.1 cubic km.  In total, about 0.21 cubic km of plagioclase-phyric dacite magma was erupted over the course of the eruption at peak effusive rates of 7 cubic metres per second in 1991. Over 2000 buildings were destroyed by these flows in Shimabara City alone. Matters were further complicated between August 1992 and July 1993 when heavy rains caused multiple lahars destroying a further 1300 homes along the Mizunashi and Nakao Rivers, requiring the sudden evacuation of several thousand residents.

Mount Unzen has been placed on the official decade volcano list and is one of Japan’s most highly monitored areas.

Maurice and Katia Krafft

The Krafft’s were French volcanologists and soul mates who met at the University of Strasbourg. Their love for volcanology almost reviled their love for each other. The specialized in documenting eruptions as best and often as close as possible, their end was almost inevitable.

Their most famed contribution was the documentation of Nevado del Ruiz which when shown to the Phillipine president Corazon Aquino who was then convinced to evacuate the area surrounding Mount Pinatubo before its catastrophic 1991 eruption almost certainly saving hundreds if not thousands of lives. 

Over a 20 year period, when volcanology was still a relativity young science, the married couple documented hundred of eruptions. They fillmed over 300 hours of footage, took thousands of photos and published multiple books.

While in the Philippines during Pinatubo’s early stages, Maurice was interviewed by a local news agency where he told the journalist  “I am never afraid, because I have seen so much eruptions in 23 years that even if I die tomorrow I don’t care.” From here they flew out to Japan where activity was picking up at Unzen. The pair perished together when they were overcome by the pyroclastic flow on June 3rd.

Harry Glicken

Man wearing a coat and hat and holding a pad of paper sits on a rock , with a lake and several mountains visible in the backgroundHarry was an American volcanologist who although was based at USGS was funded by outside organisations. He specialised in volcanic debris flows and was closely involved with research on St Helens with his doctoral thesis ‘Rockslide-debris Avalanche of May 18, 1980, Mount St. Helens Volcano, Washington‘ being recognised as a leading paper on the event.

Glicken cheated death on St Helens as he was meant to be the volcanologist on duty May 18th however swapped with his then mentor David Johnston who was killed by the blast.

Figure 1; http://raredelights.com/top-28-worlds-important-volcanoes/mount-unzen-in-japan/

Figure 2; https://curiousmatters.wordpress.com/2014/05/23/curious-facts-31-of-the-strongest-volcanoes-known-to-man/

Figure 3; https://en.wikipedia.org/wiki/Mount_Unzen

Figure 4; https://volcanogeek.wordpress.com/2011/09/20/maurice-and-katia-a-love-story/

Figure 5; https://en.wikipedia.org/wiki/Harry_Glicken

Figure 6; https://www.youtube.com/watch?v=Cvjwt9nnwXY

 

 

 

 

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Kyushu Earthquake, Mt Aso and the Relationship between Volcanoes and Earthquakes.

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In the past week the Japanese Island of Kysushu has be ravaged by earthquakes.

2016-04-16Japan is a highly seismic area with noticeable quakes in some areas occurring nearly daily.  But things began to escalate for the Kyushu region on Thursday night when a magnitude 6.5 quake brought several buildings down. As rescue efforts began the region had two more huge after shocks during the night, one over Mg 6 and the other > Mg 5. By midday Friday the death toll stood at 9 with over 800 injured and although the aftershocks kept coming many >Mg 4 people were still being pulled from the rubble. Sadly these events were quite possibly a precursor to something larger.

At 01.25 local time (15.25 GMT) a Mg 7.3 struck just north of Kumamoto just kilometers from the large earthquakes which had already occurred. Much of the seismicity in the Kyushu region is related to the subduction of the Philippine Sea plate at great depth. However this series of earthquakes have occurred at very shallow depths several hundred kilometers northwest of the Ryukyu Trench. They have been cause by strike-slip faulting within the Eurasian plate.

Quake damaged houses in Kumamoto, Japan (16 April 2016)So far 22 more people have been reported dead but this is expected to rise in the coming days with at least 80 people known to betrapped in rubble. 11 of which are trapped in a Tokai university apartment in the town of Minami Aso.

 

The shallowness of the earthquakes means damage to the surface is high and it is not just collapsing building which are a hazard. People have fled the area down stream of a dam which collapsed soon after the earthquake. Landslides in the area have taken out roads and power lines and with heavy rain anticipated over the coming days JMA have advised mudslides will be a huge problem for rescuers.

 

 

 

 

 

 

The seismic problems of Kyushu may have also set in motion another geohazard in the form of Mt Aso. Yesterday one of my favorite volcanology bloggers Eric Klemetti tweeted “Quite a few volcanoes on Kyushu and these earthquakes have been centered near Unzen, Aso, Kirishima. This is NOT to say these earthquakes will trigger any eruptions, but could be worth watching over the next year.” Several hours late JMA reported a small scale eruption at Aso. Smoke plumes have migrated 100 meters above the summit and it is not yet clear if the activity is magmatic (caused by movement of magma towards the surface) or phreatic (steam explosion caused by heating of groundwater).

Eruptions and earthquakes do not always come hand in hand but each one can contribute to the other or not at all depending on the circumstances. One indication a volcano is about to erupt is volcanic tremors; these low frequency earthquakes are usually caused by the migration of magma or changes to magma chamber. Although they are rarely higher than a magnitude 4. On the other side large earth quakes can cause faulting in bed rock which allows magma to exploit a new weakness and find a path to the surface it previously could not intrude on. The same can happen for ground water with faulting caused by a quake allowing it to seep in to geothermal areas it previously did not have access to due to the impermeability of the rock. When earthquakes hit volcanic regions volcano observatories always keep a closer eye on vulnerable or highly active volcanoes as a precaution but it is not always needed.

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The Aso Caldera complex has one of the world’s largest calderas. It is comprised of a 25 km north-south by 18 km east-west Caldera and a central cone group comprised of Mt. Neko, Mt. Taka, Mt. Naka, Mt. Eboshi, and Mt. Kishima. Mt Naka where the eruption has just taken place is the most active with its most recent eruption taking place last October. Although much of Aso’s activity in the past century has been relatively small it has had a violent history with at least 4 VEI 7 events in the past 300,000 years.

It’s is not clear whether the earthquakes in the past few days did trigger the current current eruption but JMA are keeping a close eye on the situation and I will update this page as I know more.

 

 

Figure 1. http://earthquake.usgs.gov/earthquakes/map/

Figure 2; http://www.bbc.co.uk/news/world-asia-36061657

Figure 3; http://www.independent.co.uk/news/world/asia/japan-earthquakes-dozens-reported-dead-injured-second-quake-two-days-a6986931.html

Figure 4; http://mashable.com/2016/04/15/japan-earthquake-landslide-photos/

Today in Geological History; March 11th – Tōhoku Earthquake & Tsunami

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article-0-0D924D9F000005DC-785_964x591.jpgI am pretty sure I have covered this event before but seeing as today marks the 5 year anniversary of one of the worst natural disasters in the past decade I thought it deserves a much more in depth look. The events of March 11th destroyed the lives of hundreds of thousands of people and claimed the lives of nearly 20,000. For me, it opened my eyes to a world of geohazards and mad me realized this was something I wanted to study and understand so such loss of life would not happen again.

There are three elements to the events of March 11th that I am going to look at here; the earthquake, the tsunami and the Fukushima power plant. Each aspect a huge disaster in on there own but interlinked as they were caused devastation for Japan. 

The Earthquake

Instrumental Intensity Image

Japan is a volcanic island which stretches along where the North American, Pacific, Eurasian and Philippine plates all collide at different points. It is a part of the Pacific Ring of Fire, the world’s most tectonically active area. Practically all of our planets largest and most destructive earthquakes occur along the ring, one of which rocked the east coast of Japan at 2.46 pm JST (5.46am UTC) on March 11th 2011.

The magnitude 9 quake struck at the shallow depth of just 32 km roughly 70 km off the Oshika Peninsular. The area was already alert to seismic activity as several large foreshocks had occurred in the run up including a Mg 7.2 on March 9th and followed by three more above a Mg 6. Of course no one knew these were precursors to something much larger…

Initial reports from JMA and USGS put the March 11th quake at a 7.9 but this had risen first to a 8.8 and then to a 9 before most of the seismic waves had even hit Tokyo 373 km away. Luckily thanks to Japans intense seismic network the countries capital had at least 80 seconds warning before they felt the strong shaking.

The megathrust earthquake occurred where the Pacific Plate subducts beneath the North America Plate. The Pacific Plate moves at a relative speed of roughly 9 mm per year but it is not a smooth decent, tension can build and release in a large snap causing an earthquake. On March 11th this happened in epic style causing over ~50 meters of displacement near the Japan Trench which caused the tsunami which swept across the Sendai planes. The earthquake was so powerful that up to 1.69 meters of co-seismic deformation has permanently altered our planet and affected the Earths tilt shaving 1.8 microseconds of the day (not that we would ever notice!)

It was the forth largest earthquake ever recorded and the largest ever to strike Japan.

The Tsunami 

The displacement on the sea bed in turn caused a huge displacement of water in the Pacific ocean its self. Across a 180 km stretch there was recorded up thrust of 6-8 meters. Above the rupture the tsunami waves would have looked like no more than ripples on the surface radiating out across the ocean. It is as the waves reach the continental shelf and the water is forced upwards that they begin to take on their characteristic ‘wall of water’ appearance.
At its maximum height (recorded at Miyako, Iwate) the waves hit 40.5 m high (133 ft). The Pacific has the most comprehensive tsunami warning systems in the world but even this gave only about 15 minutes warning from the earthquake to waves hitting the coast line. Travelling at speeds up to 500 mph the water surged up to 6 miles (10 km) inland.

Honshu earthquake tsunami travel times

It was not just Japan which felt the repercussions of the event. Tsunami waves propagated out through out the entire Pacific. 11,000 miles away the coast of Chile experienced waves in excess of 2 meters along with most of the America west coast right up through to the Aleutian Islands and as far south as Antarctica where it broke chunks off the Sulzberger Ice Shelf

An estimated 5 million tonnes of debris began washing up on shore lines across the Pacific in the months and even years after the initial Earthquake. In April 2013 a 20 ft boat ran aground in California and was later identified as belonging to the marine sciences program at Takata High School, Japan. NOAA have kept tracks and aimed to clear as much of the debris as possible to minimize risk to ships and wild life but the operation can take more than a decade.

Fukushima

The melt down at the Fukushima was the worst nuclear disaster the world has seen since Chernobyl in 1986.

The plant ran by TEPCO had 3 of its 6 units shut down for inspection when the earthquake struck. Units 1, 2 and 3 then under went automatic shutdown cutting off power. 50 minutes later the waves up to 15 meters high breached the measly 5.7 meters seawalls and flooded the basements of the turbine buildings and disabling the emergency generators. The lack of power meant the cooling systems of the 3 active reactors failed and eventually the heat caused by decay caused the containers to burst leaking radioactive material.

It was classified a Level 7 on the International Nuclear Event Scale (INES) and its was the way the event was handled from the very beginning my TEPCO which saw the escalation in the threat. Approximately 15 PBq of caesium-137 was released along with some 500 PBq of iodine-131, luckily all the failed reactors were in concrete containment vessels, which limited the release of strontium-90, americium-241 and plutonium.

Dozens of vehicles lie abandoned and covered in overgrown bushes along what was once a stretch of road near the power plantNo deaths were caused by the events or short term radiation exposure but it is thought people in the area worst hit will have a slightly higher risk of developing certain cancers in the future. Now 5 years on there is still a 12.5 km is still in place with thousands of people still exiled from their homes. The wild has reclaimed the land making it look like a scene from an apocalyptic film.

It could be centuries before the area is truly deemed safe to live on again.

Pre-Warning; This has happened before

Japan is no stranger to tsunamis; the 1896 and 1933 Sanriku earthquakes (Mg 8.5 and 8.4 respectively) also brought deadly waves. For this reason tsunami barriers have been constructed both on and off shore, trees were planted along the coastline, vertical evacuation buildings were built to the highest standards and regular evacuation training was introduced. But none of these were built to with stand the sheer force of a tsunami of this magnitude.

In 2001 a team from Tohoku University published an article in Journal of Natural Disaster predicting such an event occurring every 800-1100 years. Within the Sendai Plain there is evidence of at least 3 major tsunami deposits all left within the past 3000 years. On July 9th 869 BC what is believed to be a magnitude 8-9 earthquake occurred off the coast of Sanriku causing a major tsunami which left deposits up to 4 km inland. So given that we knew an event like this had occurred before, why was Japan not better prepared for March 11th?

Sadly human nature does not always listen to the reason of science. It is often easier to believe ‘it won’t happen in my life time’ and then brush the threat under the carpet for future generations. The problem is it does not matter how much we study the mechanics of our planet we are still no where near being able to predict these disasters with any degree of accuracy meaning preparation is our best defence.

Aftermath

A report issued by the Japanese government in May 2015 claimed the events of March 11th 2011 caused $300 billion dollars. A confirmed 15,894 people lost their lives, 2,562 people are still unaccounted for.

5 years on the area is yet to recover. An estimated 174,000 are still displaced mainly due to the exclusion zone still heavily in place around the Fukushima plant. Soon as the initial rescue operation was completed the Tohoku Earthquake Tsunami Joint Survey Group was assembled. A team of natural scientists and engineers from 63 universities world wide set out to understand what made this tsunami so powerful and how we can protect our selves from further events. By the end of 2011 the Japanese government had passed laws to establish “tsunami-safe cities” and pledged billions of dollars to an intense 5 year clean up operation. It was clearly a bigger job than they originally thought….

Today there are still over 60,000 people living in temporary accommodation.For residents once living near the Fukushima power plant they will probably never return to there own homes. Sendai is still trying to recover from the tragic events but also now living in fear that this could occur again.

It is for this reason I choose to go in to studying geoscience. We all live at the mercy of our planet and most of us never even consider the risk the land beneath our feet poses. Prediction, preparation and knowledge can save lives and this is what I one day want to help with.

 

Figure 1; http://www.dailymail.co.uk/news/article-1365318/Japan-earthquake-tsunami-The-moment-mother-nature-engulfed-nation.html

Figure 2; http://earthquake.usgs.gov/earthquakes/shakemap/global/shake/c0001xgp/

Figure 3; http://minookatap.com/2011/08/22/japan-book-club-the-big-wave-5/

Figure 4; http://www.livescience.com/39110-japan-2011-earthquake-tsunami-facts.html

Figure 5; https://7plaguesofgod.wordpress.com/2011-tsunami-japan/

Figure6; http://vassarchronicle.com/section/politics/foreign-affairs/lack-of-regulation-fukushima-meltdown/

Figure 7; http://www.dailymail.co.uk/news/article-3263714/Destroyed-man-reclaimed-nature-Amazing-images-reveal-exclusion-zone-Fukushima-abandoned-overgrown-wilderness.html

 

 

 

The Decade Volcanoes

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As I reblogged my last post, a revision of the Decade volcano list by the authors of VolcanoCafe, I thought before I bring you the new list I should really explain what the original one actually was!

As mentioned in one of my earliest articles, the list was complied in 1990 by the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) a nongovernmental society. The aim was to select the worlds most hazardous volcanoes and put measures in place to keep a closer eye on them and raise awareness across the globe on the threats they pose, for a decade (1991-2000 The UN’s International Decade of Natural Disaster Reduction). Based on varied criteria from historic eruptions to local populations, the following made the cut;

Figure 1. USGS map of the decade volcanoes.

15 Years on the list is still going all though monitoring in some areas may have slackened slightly. It has seen some success such as the diversion of a lava flow on Etna back in 1992 and has helped form a better understanding of phreatic eruptions on Taal. It has sadly also come at great loss on several occasions as well. Despite increased monitoring of Unzen in 1991 pyroclastic flows killed 43 including volcanologists Katia and Maurice Krafft and Harry Glicken.  And even closer to the project, in 1993 the Decade Volcano conference took place in Pasto, Columbia an expedition from the conference to the Galeras crater occurred on February 14th when the volcano suddenly erupted. 3 tourists and 6 volcanologists including Professor Geoff Brown, Head of Department of Earth Science at the Open University, all lost their lives.

Many volcanologist are sceptics and/or critics of the program, hence the call for a revamp. Personally I feel any thing which promotes volcanic awareness is great all though there are some which need much more than others. Volcanoes are ever evolving and unlike most geological features can change in minutes rather than millennia and therefore prehaps a decade is too long for reviews of such a program. I know which have made my list, it will be interesting to see what makes the cut for the guys at VolcanoCafe!

Figure 1. http://listas.20minutos.es/lista/volcanes-de-la-decada-decade-volcanoes-301649/

What Makes an Earthquake ‘Significant’?

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If you google “What is the definition of a significant earthquake?” you are met with Michigan Tech’s* response; Major – magnitude 7-7.9. However when looking at ‘significant’ earthquakes on the USGS** web page there are ones as low as magnitude 3.3. So to different people (and/or institutions) how we classify earthquakes seems to vary greatly and this occurs from top seismologists right through to media reporting and how we perceive the threat.

 

At 11.23 UTC on May 30th a Mg 7.8 earthquake struck off the coast of Japan. This is the same magnitude as that of Nepal’s April 25th quake but one managed to devastate an entire region and the other barely shook a few skyscrapers. Unless, like my self you concern your selves with the rumblings of our planet, or you live in Japan or the surrounding area you probably did not ever know last Saturdays earthquake even happened.

1. Aftermath of Nepal earthquake April 25th 2015.

The main difference between the two is the location of their foci. The focus of an earthquake (sometimes called the hyprocenter) is often confused with the epicentre, however the epicentre is the surface area directly over where the earthquake takes place, whereas the focus is the actual point at depth where the snap of energy takes place. With the Nepal earthquake the focus was just 15 km under a heavily populated region. The buildings on the surface were poorly built and unable to with stand the violent shaking, bringing them crumbling to the ground killing over 8000 people.

2. Displacement by Japan’s March 11th 2011 earthquake.

The Japan earthquake in contrast occurred off the coast, below the Pacific Ocean, although the some shaking was felt onshore. Many may assume this is safer than an earthquake under an urban area but several of the most deadly earthquakes occur at sea as they can induce tsunamis like that of March 11th 2011 which killed nearly 30,000 in Japan or the infamous Boxing Day Tsunami which killed as many as 230,000! Luckily on Saturday no tsunami alert was even issued, as the biggest difference between these two 7.8 earth quakes is depth.

Occurring at 677 km beneath the surface, this deep-focus (below 300 km) earthquake happened so deep its distance from focus to surface is only slightly shorter than travelling from London to Berlin (690 km)!!! As seismic waves travel they dissipate, loosing energy so are never as intense as what they are closer to the source.

3. Diagram of an earthquake, highlighting its focus and Epicenter.the waves lighten in colour with distance from the focus to show their loss of strength.

 

So so far we have magnitude, depth and location which impact on the devastation potential, but is there any thing else? Well we can expand on the last, location, to highlight other potential threats posed by an earthquake. A moderate sized earthquake in the heart of Los Angeles or Tokyo may stop the subway and send food flying off shop shelves but casualties should be low. The same earthquake in a country like Nepal or Haiti can kill thousands. Earthquakes don’t kill people per say, I have never heard of some on being shaken to death by a quake.What kills people is poorly constructed buildings collapsing, bridges failing, gas mains bursting causing fires. After past disasters such as San Fransisco’s great earthquake of 1906, wealthy countries which sit along active fault lines have put in place strict building codes and pumped millions in to disaster management programs and construction.   Obviously earthquake-proof is not always a possibility by earthquake-resistant definitely is and has saved the lives of many of the past few decades. Sadly not all at risk areas have that luxury of these safe guards at the expense of hundreds of lives.

4. Damage and fires caused by the Greath San Fransisco earthquake in 1906.

Seismology is a tricky business. With so much to take in to consideration when classify earthquakes, it is easy to see where there is often conflicting statements. Things are complicated further by the multitude of scales actually used to quantify them. When asked what scale is used, I can guarantee most will say the Richter scale (or local magnitude, ML), that is even what I was taught in school. Charles Richter first put his scale to use in 1935 to give a more scientific quantification for earthquakes than the previously used Mercalli scale which was solely based of human perspective and building damage (this is still used today but not as often). The Richter scale was limited in many ways being primed for nearby, mid-sized earthquakes (M 3-7). Seismologist Beno Gutenberg expanded on Richter’s work greatly enabling the scale to factor in greater distances and separated scales for surface waves (MS) and body waves (Mb).The revised scales still had difficulties and were particularly ineffective when looking at earthquakes which spanned great lengths of fault lines such the Aleutian Fox Island quake of 1952. The Richter scale was finally replaced by the Moment magnitude scale (MW) back in 1979 and this is the scale used by most institutes today including USGS.

Moment magnitude was born from elastic dislocation theory put forward in 1972 which suggests that energy release from a quake is proportional to the surface area that breaks free, the average distance that the fault is displaced, and the rigidity of the material adjacent to the fault. It is based on a similar logarithmic scale to the Richter scale with each step equating to an increase in the amount of energy released 101.5 ≈ 32 more than the previous. Earthquakes usually have similar Richter and moment magnitude numbers but rarely exactly the same and this can be one way one earthquake can be reported at different levels across the media if their sources used different scales. Another way which causes different figures  is precision; the more seismic stations used to calculate magnitude the more precise the result. When an earthquake is first recorded institutes are likely to only use their own data but as soon as they have access to the global seismic network they can give a more accurate classification. This happen with Japan’s earthquake on May 30th, initial reports put it over a magnitude 8 but this was quickly downgraded to 7.8.

As you can see an earthquakes significance is a matter for debate and in many cases personal opinion. Magnitude and location (not just geographically but also politically) are the main factors but it tends to vary earthquake to earthquake.

Station VRI seismogram

5. Example of a seismograph.

 

Eruptions Update

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Turrialba

Costa Rica’s Turrialba has been rumbling for about a week now and at 9pm UTC Monday 4th it gave a moderate eruption which has coated as far as the country’s capital, San Jose, in ash 60km away. An ash column stood at just 2.5 km in from the eruption which lasted little over half an hour. The Juan Santamaría International Airport was closed for under 12 hours as staff worked through to clear the run way of ash, the aviation code has since been lowered and flights have resumed normal operation. When Turrialba started erupting back in March it left the airport closed for days, luckily this seems to be a much smaller eruption.

Turrialba, Costa Rica

Bulusan

Bulusan in the Philipeans let off a small phreatic eruption at 1.30 local time on Friday 1st May. The eruption which only lasted 5 minutes was followed by 40 volcanic tremors. Philvolcs have left the alert at 0 with it belived further activity is unlikely but the 4 km permanent danger zone is being kept in place. Local residents have also been advised to be watchfull of lahars and sediment heavey stream flows due to the heavy rain in region.

Hakone

JMA are sending a team to look in to increased seismicity in the Hakone hot springs region. The earthquakes are believed to volcanic tremors which have been increasing at a shallow depth since late April. Inflation of the volcanic edifice is also being looked into. Alert remains low.

 

 

Mg 6.9 Iwate and Tsunami warning

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At 8.06 am local time a magnitude 6.9 submarinal earthquake occurred of the coast of Iwate, Japan. JMA have claimed it is an after shock from the mg 9, March 11th megathrust quake in 2011.

The following tsunami alert was released although this was played up by some media stations to a full blown warning.

This Tsunami Warning/Advisory was issued in the past
Occurred at 08:06 JST 17 Feb 2015
Region name Sanriku Oki
Depth about 10 km
Magnitude 6.9
Click the map to zoom in

Tsunami Forecast Region Category of Tsunami Warning/Advisory
IWATE PREF. TSUNAMI ADVISORY

Tsunami Warnings / Tsunami Advisories

Issued at 08:09 JST 17 Feb 2015

******************Headline******************
Tsunami Advisories have been issued for the following coastal regions of Japan:
IWATE PREF.

*******************Text********************
Tsunami Advisories have been issued for the following coastal regions of Japan:
<Tsunami Advisory>
IWATE PREF.

***********About Tsunami Forecast************
<Tunami Advisory>
Marine threat is in place.
Get out of the water and leave the coast immediately.
As the strong current will continue, do not get in the sea or approach coasts until the advisory is cleared.

<Tsunami Forecast (Slight Sea Level Change)>
Though there may be slight sea-level change in coastal regions, no tsunami damage is expected.

******* Earthquake Information ********
Occurred at 08:06 JST 17 Feb 2015
Region name SANRIKU OKI
Latitude 39.9N
Longitude 144.5E
Depth about 10 km
Magnitude 6.9

The following arrival times were issued;

Tsunami Forecast Region/
Tsunami Observation Site
High Tide Time Estimated Initial
Tsunami Arrival Time
<Tsunami Advisory>
  IWATE PREF. ( Area where tsunami is
expected to arrive first )
08:30 JST 17 Feb
    Miyako 13:28 JST 17 Feb 08:40 JST 17 Feb
    Ofunato 13:36 JST 17 Feb 08:40 JST 17 Feb
    Kamaishi 13:36 JST 17 Feb 08:40 JST 17 Feb
    Kuji-ko 13:23 JST 17 Feb 08:50 JST 17 Feb

The warning was then terminated at 10.21 local time.