March 11, 2011 Japan Earthquake—10th Anniversary—Lessons Learned (educational)
Summary
TLDRThe video script delves into the 2011 Tohoku-oki earthquake, Japan's largest in history, detailing its catastrophic impact and the scientific insights gained. It highlights the importance of tsunami geology, earthquake early warning systems, and the integration of GPS with seismometers for improved accuracy in warnings. The script also underscores the significance of public education in disaster preparedness, emphasizing the 'Drop, Cover, and Hold On' protocol during earthquakes and the natural tsunami warning they provide.
Takeaways
- 🏔 Honshu is the largest of Japan's three major islands and is located on the Pacific Ring of Fire, making it prone to significant seismic activity.
- 🌊 The Tohoku region of northern Honshu experienced a devastating M9 earthquake on March 11, 2011, which resulted in a massive tsunami and nearly 20,000 lives lost.
- 💡 Tsunami geology can extend the earthquake record by centuries or millennia, providing insights into past seismic events.
- ⚠️ Earthquake Early Warning systems can mitigate damage and save lives but have limitations, as seen in the 2011 Tohoku earthquake.
- 📍 The integration of Global Positioning System (GPS) observations with seismometer data improves the accuracy of earthquake early warning systems and is crucial for tsunami warnings.
- 🔍 Historical and geological evidence suggests that the subduction plate boundary could store elastic energy over 1000-year intervals before releasing it in a large earthquake.
- 🌋 The 2011 Tohoku-oki earthquake revealed that the megathrust plate boundary could produce earthquakes with magnitudes up to 9, much larger than previously thought.
- 🔬 High-precision GPS monitoring is essential for understanding the mechanics of plate boundaries and the potential for large earthquakes.
- 🏞️ The uplift and subsidence of the seafloor due to the earthquake's fault slip generated the tsunami that caused widespread damage and loss of life.
- 🏗️ Japan's stringent building codes and quality construction practices, along with its earthquake early warning system, saved many lives despite the earthquake's severity.
- 🚀 Advances in GPS and seismic network integration, such as Japan's GEONET, have improved the speed and accuracy of earthquake and tsunami warnings.
Q & A
What is the largest island in Japan?
-Honshu is the largest of the three major Japanese islands.
Which region of Honshu has three prefectures facing the Pacific Coast and the Japan Trench?
-The Tohoku region of northern Honshu has three prefectures on the Pacific Coast directly facing the Japan Trench.
What is the rate at which the Pacific Plate descends into the Japan Trench beneath the Okhotsk Plate?
-The Pacific Plate descends into the Japan Trench and beneath the Okhotsk Plate at a rate of 8.3 cm/yr.
When did the M9 Tohoku-oki earthquake occur?
-The M9 Tohoku-oki earthquake occurred just after 2:46 PM local time on March 11, 2011.
What were the consequences of the 2011 Tohoku-oki earthquake and tsunami?
-The 2011 Tohoku-oki earthquake and resulting tsunami took almost 20,000 lives and caused approximately $200 billion in damage.
How can tsunami geology contribute to understanding earthquakes?
-Tsunami geology can extend the earthquake record by centuries or millennia, providing a longer-term perspective on seismic activity.
What limitations were revealed by the 2011 earthquake in the Earthquake Early Warning system that uses only seismometers?
-The 2011 earthquake revealed limitations of a system using only seismometers, such as the inability to rapidly determine fault slip or final magnitude, which is crucial for accurate tsunami warnings.
How does the addition of GPS observations improve earthquake early warning systems?
-Adding Global Positioning System observations of earthquake ground motion improves the accuracy of earthquake early warning and is essential to tsunami warnings by providing more precise data on fault slip and ground movement.
What is the historical significance of the 869 A.D. earthquake and tsunami in the context of the Tohoku-oki earthquake?
-The 869 A.D. earthquake and tsunami are significant because they indicate that the subduction plate boundary could store elastic energy over 1000-year intervals and then release it in a megathrust earthquake of magnitude 8.5 or even up to 9.
How did the high-precision GPS monitoring provide insights into the mechanics of the plate boundary before the Tohoku-oki earthquake?
-High-precision GPS monitoring showed that stations across northern Honshu were being pushed westward at up to 3 cm/yr, indicating that the megathrust has high friction and could store elastic energy over many centuries.
What improvements have been made to earthquake and tsunami warning systems based on the lessons learned from the 2011 Tohoku-oki earthquake?
-Improvements include the installation of GPS networks, advances in precision and speed of receivers, integration of GPS and seismic networks, and the installation of the S-net cabled system of ocean bottom seismometers and pressure gauges for earlier and more accurate warnings.
Outlines
🌏 The Tohoku Earthquake and Tsunami: A Lesson in Geology and Preparedness
This paragraph discusses the devastating impact of the M9 Tohoku-oki earthquake that struck Japan on March 11, 2011, resulting in nearly 20,000 casualties and $200 billion in damages. It highlights the importance of tsunami geology in extending the earthquake record, the limitations of earthquake early warning systems, and the necessity of integrating Global Positioning System (GPS) observations for improved accuracy in earthquake and tsunami warnings. The paragraph also underscores the significance of public education in earthquake and tsunami preparedness, emphasizing the simple yet effective 'Drop, Cover, and Hold On' protocol, and the importance of moving to higher ground in the event of a coastal earthquake. The historical context of the earthquake is provided, including the discovery of a sand layer indicating a massive tsunami in 869 A.D., and the subsequent research that suggested the potential for a megathrust earthquake of magnitude 8.5 or greater. The paragraph concludes with an explanation of how high-precision GPS monitoring can offer insights into plate boundary mechanics and the storage of elastic energy over centuries, which was released during the 2011 earthquake.
📡 Advancements in Earthquake and Tsunami Warning Systems
The second paragraph delves into the specifics of the Tohoku-oki earthquake's impact, noting the areas most affected and the fatalities that occurred. It describes the fault rupture's spread and the minimal number of deaths outside the tsunami zone, attributing this to Japan's advanced earthquake engineering and building practices. The paragraph also examines the limitations of Japan's earthquake early warning system during the Tohoku-oki earthquake, which was unable to accurately predict the magnitude and resulting tsunami height due to its reliance on seismometer data alone. The narrative then pivots to discuss improvements in warning systems, including the integration of GPS networks with seismic networks, exemplified by GEONET in Japan. The power of combining GPS and seismometer observations is illustrated through the case study of the 2011 earthquake, where GPS stations recorded significant movements. The paragraph concludes with the introduction of the S-net cabled system, which offers earlier earthquake warnings and more accurate tsunami forecasts by utilizing instruments on the ocean floor above the plate boundary megathrust.
Mindmap
Keywords
💡Honshu
💡Subduction Zone
💡Tohoku-oki Earthquake
💡Tsunami
💡Earthquake Early Warning (EEW)
💡Global Positioning System (GPS)
💡Megathrust Earthquake
💡Geoscientists
💡Plate Tectonics
💡S-net
💡GeoNET
Highlights
Honshu is the largest of the three major Japanese islands with a subduction zone boundary.
The Tohoku region of northern Honshu faces the Japan Trench with three prefectures on the Pacific Coast.
The Pacific Plate descends into the Japan Trench at a rate of 8.3 cm/yr.
The M9 Tohoku-oki earthquake on March 11, 2011, resulted in nearly 20,000 lives lost and $200 billion in damage.
Tsunami geology can extend the earthquake record by centuries or millennia.
Earthquake Early Warning systems can mitigate damage and save lives but have limitations.
GPS observations improve the accuracy of earthquake early warning and are essential for tsunami warnings.
Lessons from the 2011 Tohoku-oki earthquake are being applied to global earthquake and tsunami warning systems.
Public education is crucial for earthquake and tsunami preparedness.
Basic safety measures during an earthquake include 'Drop, Cover, and Hold On'.
An earthquake near the ocean serves as a natural tsunami warning, prompting evacuation to higher ground.
Historical earthquake data suggests that magnitudes might not exceed 8.2 on the megathrust plate boundary.
Geoscientists discovered evidence of an 869 A.D. earthquake and tsunami with a magnitude of at least 8.4.
High-precision GPS monitoring provides insight into plate boundary mechanics and energy storage.
The 2011 Tohoku-oki earthquake demonstrated the potential for energy storage over centuries in a subduction zone.
The earthquake's rupture started 24 km beneath the seafloor and propagated in both directions.
Fault slip of over 60 meters at the Japan Trench is the largest documented in modern history.
The tsunami from the earthquake reached inundation heights of 20 meters on the Sendai Plain.
Japan's earthquake engineering, building codes, and construction practices saved thousands of lives.
Japan's early warning system issued warnings 14 seconds before strong shaking in Sendai.
The early warning system's limitations were exposed by the inability to rapidly determine fault slip or final magnitude.
Integration of GPS and seismic networks, like GEONET in Japan, improves earthquake and tsunami warnings.
The S-net system of ocean bottom seismometers and pressure gauges enhances subduction zone monitoring.
S-net can provide earlier earthquake warnings and more accurate tsunami forecasts for coastal communities.
Transcripts
Honshu is the largest of the three major Japanese islands. The Tohoku region of
northern Honshu has three prefectures on the Pacific Coast directly facing the Japan
Trench. At this subduction zone boundary, the Pacific Plate descends into the Japan Trench
and beneath the Okhotsk Plate at 8.3 cm/yr. The M9 Tohoku-oki earthquake occurred just
after 2:46 PM local time on March 11, 2011. This great earthquake and resulting tsunami took almost
20,000 lives and caused approximately $200 billion damage. Scientific lessons
learned and described here include: 1. Tsunami geology can extend the
earthquake record by centuries or millenia. 2. Earthquake Early Warning can mitigate damage
and save lives, but the 2011earthquake revealed limitations of a system using only seismometers.
3. Adding Global Positioning System observations of earthquake ground motion
improves accuracy of earthquake early warning, and is essential to tsunami warnings.
These seismology and geodesy lessons from the 2011 Tohoku-oki earthquake are being
applied to earthquake and tsunami warning systems worldwide. However, these technical
advances are necessary but not sufficient to advance earthquake and tsunami preparedness.
Public education is essential and often the most basic lessons are the most empowering.
During an earthquake, Drop, Cover, and Hold On. If you are near the ocean,
the earthquake is your natural tsunami warning. Move quickly away from the shore to high ground
Now let’s dig into the plate tectonics and earthquake history.
A cross section through the March 11 epicenter shows the Pacific Plate
subducting beneath the Okhotsk Plate. Before 2011, what observations did we have about
earthquakes on this megathrust plate boundary? For each earthquake of magnitude 7.4 and larger
earthquakes from 1896 to 2010, the year and rupture area of the plate boundary that moved
during the earthquake are shown along with the earthquake magnitude. This history suggests
that earthquake magnitudes might not exceed 8.2. But research in the decade before the
Tohoku-oki earthquake led some seismologists to conclude that an earlier earthquake
with magnitude of at least 8.4 had caused a massive tsunami that inundated the Sendai plains.
Geoscientists found a sand layer they interpreted as having been deposited by that tsunami.
Historical documents revealed that this earthquake and tsunami occurred in 869 A.D. . This geologic
evidence suggested the subduction plate boundary could store elastic energy over
1000-year intervals then release that energy in a megathrust earthquake of magnitude 8.5
or perhaps even up to magnitude 9, 25 times more energy than any earthquake since 1896.
How could they test their hypothesis that energy was being stored? Compression of the
overriding plate stores elastic energy similar to a spring when the coils are pushed together.
High-precision GPS monitoring can provide insight into the mechanics of a plate boundary.
Seismologists determined that motion between the Pacific and Okhotsk plates during earthquakes of
the past few centuries was much less than the relative
plate motion. And across northern Honshu, GPS observations from 1990 to 2010 showed
stations being pushed westward at up to 3 cm/yr, indicating that the megathrust has high friction.
So, this subduction zone could store elastic energy over many centuries
then rebound during a massive earthquake. As it did on March 11, 2011.
Rupture started 24 km beneath the seafloor at the hypocenter, then propagated both up
to the east and down to the west. Fault slip of 40 meters at the hypocenter and
over 60 meters at the Japan Trench are the largest documented for any earthquake in modern history.
The 40-km-wide seafloor slope west of the trench uplifted 10 meters while the seafloor near the
coast dropped 2 meters. These offsets of the ocean floor produced the tsunami that rushed
onshore starting 30 minutes after the earthquake. Inundation height reached 20 meters on the Sendai
Plain, the most populous area in Tohoku. Tsunami runup in some locations reached 40
meters! Fatalities plus missing, concentrated in Iwate, Miyagi, and Fukushima prefectures,
totaled almost 20,000. In map view,
fault rupture spread from the epicenter to cover an area 500 km long by 200 km wide
in just over 2 minutes. Fault slip was greatest between the epicenter and the Japan Trench.
Despite minutes of strong to severe ground shaking, fewer than 50 fatalities occurred outside
of the tsunami zone. Centuries of experience with earthquakes, world leadership in earthquake
engineering, stringent building codes, and quality construction practices saved thousands of lives.
Japan’s earthquake early warning system also decreased impacts of earthquake ground shaking.
the Earthquake warning system, in place prior to the Tohoku-oki earthquake,
used a dense network of broadband seismometers that detects P waves from an earthquake,
locates the epicenter, estimates magnitude, then provides warnings before potentially damaging S
waves and surface waves arrive. This works reasonably well for magnitude 6 or 7 earthquakes
within or near the seismometer network. This was not the case for the March 11 quake.
Just after 2:00PM, P waves reached seismometers on the coast, 22 seconds after the initial rupture.
An early warning was issued to advanced users at 30 seconds and to the public at 31 seconds,
14 seconds before strong shaking arrived in Sendai. Numerous protective actions
such as slowing Shinkansen trains, alerting fire, police, and emergency personnel, and
alerting hospitals were taken and those measures decreased damage, injuries, and fatalities
A warning system based on broadband seismometers, can notify you that an earthquake has occurred,
but it cannot rapidly determine fault slip or final magnitude.
Even when rupture was nearly complete, magnitude was estimated at 8.0
As a result, tsunami alerts issued at 3 minutes grossly underestimated wave heights.
To make matters worse, power outages limited communications.
How can we improve these earthquake and tsunami warnings?
Installation of GPS networks and advances in precision and speed of receivers
has led to the integration of the GPS and seismic networks. GEONET in Japan is a leading
example. As more and larger earthquakes have been recorded by GPS networks, the power of combining
GPS with seismometer observations has emerged. The 2011 Tohoku-oki earthquake is the case study.
During the earthquake, GPS stations across northern Honshu moved toward the area of
greatest fault slip by as much as 5 meters. For example, Station 0172
moved 2 meters south and 4 meters east between 50 and 100 seconds after megathrust rupture started.
A network of seismometers alone, as used by the Earthquake Early Warning system in 2011,
cannot determine a fault-slip model for a great megathrust earthquake
or accurately forecast tsunami wave heights in time to issue useful tsunami warnings
Several research teams have shown that combined seismometer and GPS ground motion data
could be analyzed to determine a reasonably accurate fault-slip model
for the Tohoku-oki earthquake within 90 seconds from initiation of rupture.
Installation of the S-net cabled system of ocean bottom seismometers and pressure gauges
stations has taken subduction zone earthquake and tsunami monitoring a giant step further.
With instruments on the ocean floor directly above the plate boundary megathrust,
S-net can provide earthquake early warning 20 to 30 seconds sooner than land-based networks.
And measurements of tsunami heights in the source area can provide
accurate tsunami forecasts more than 30 minutes before a tsunami reaches coastal communities.
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