The Strongest Earthquakes Ever Recorded: The Day Chile Shortened the Day

The strongest earthquake ever recorded was the 1960 Valdivia earthquake in Chile, at magnitude 9.5. It released so much energy that it measurably altered Earth's rotation and made the whole planet vibrate for weeks. Every one of the most powerful quakes shares the same birthplace, the magnitude scale that ranks them is far more deceptive than it looks, and the reasons a fault can grow to planet-shaking size come down to plate geometry you can trace on a map. This guide walks through the full ranking, the physics of why magnitude numbers lie to your intuition, and what separates a quake that merely shakes a city from one that rings the Earth like a bell.

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The Short Answer: Strongest Earthquakes (by Magnitude)

Rank	Earthquake	Magnitude	Year	Location
1	Valdivia (Great Chilean)	9.5	1960	Biobío/Chile
2	Great Alaska (Good Friday)	9.2	1964	Prince William Sound, Alaska
3	Sumatra–Andaman	9.1	2004	Off northern Sumatra, Indonesia
4	Tōhoku	9.1	2011	Japan Trench, offshore Honshu
5	Kamchatka	9.0	1952	Kamchatka Peninsula, Russia
6	Kamchatka	8.8	2025	Kamchatka Peninsula, Russia
7	Maule	8.8	2010	Biobío, Chile
8	Ecuador–Colombia	8.8	1906	Esmeraldas, Ecuador
9	Rat Islands	8.7	1965	Aleutian Islands, Alaska
10	Assam–Tibet	8.6	1950	Arunachal Pradesh, India

Table: The ten largest earthquakes ever recorded by moment magnitude, according to United States Geological Survey (USGS) records. USGS

These are the only earthquakes ever measured at magnitude 8.6 or above since modern seismographic instruments began recording global events in the early twentieth century, and the gap between rank one and the rest of the list is far larger than the numbers on the page suggest. That gap is the whole story of this article: why a 9.5 isn't "slightly bigger" than a 9.0, why nearly every name on that table sits on the Pacific Rim, and why the deadliest of these quakes are often deadly for a reason that has nothing to do with the shaking itself.

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Why the Magnitude Scale Fools People

Every earthquake on the list above is measured on the moment magnitude scale (Mw), the modern successor to the old Richter scale. It was developed in 1979 by seismologists Thomas Hanks and Hiroo Kanamori specifically because the original Richter scale, built in the 1930s for small local quakes in Southern California, badly underestimated the size of the very largest earthquakes on the planet (Hanks & Kanamori, 1979, Journal of Geophysical Research).

Moment magnitude is calculated from the seismic moment — a physical quantity that combines three things measured directly from the fault itself: the rigidity of the rock, the total area of the fault that ruptured, and how far the two sides of the fault slipped past each other. The formula is Mw = (2/3)log₁₀(M₀) − 10.7, where M₀ is the seismic moment. That two-thirds exponent is the source of everything counterintuitive about the scale.

Because the scale is logarithmic, two simple rules govern how these numbers behave:

• Each whole number increase means about 10 times more ground-shaking amplitude. A magnitude 8 shakes the ground roughly ten times more than a magnitude 7, at the same distance from the source.
• Each whole number increase means roughly 32 times more energy released. The exact multiplier is 10^1.5, or about 31.6.

Think of it the way you'd think of a savings account earning compound interest rather than simple interest. A linear scale would mean going from magnitude 8 to magnitude 9 releases one unit more energy, like adding a fixed dollar amount every year. A logarithmic scale means each step multiplies the previous total, the way compound interest multiplies your balance rather than adding to it. Skip two steps, from magnitude 7 to magnitude 9, and you've multiplied the energy by roughly 1,000, not by 200.

The 1960 Chile earthquake at magnitude 9.5 released more seismic energy, by most estimates, than every other earthquake recorded during the entire twentieth century added together. That single event on a single day outweighs a hundred years of everything else measured by instruments.

This is exactly why a "magnitude 6" earthquake can flatten a poorly built city while a "magnitude 9" sounds only modestly larger on paper but sits in an entirely different universe of destructive power. It's the same logarithmic trap that shows up when scientists compare the biggest explosions in history — a scale where numbers that look close together on paper represent wildly different quantities of released energy underneath.

Why isn't the Richter scale used anymore?

The Richter scale (local magnitude, ML) measures the amplitude of seismic waves recorded on a specific type of instrument at a specific distance from small-to-moderate quakes. It "saturates" above about magnitude 7, meaning it can't distinguish between a magnitude 8 and a magnitude 9.5 event because the biggest fault ruptures generate low-frequency waves the original instrument couldn't register accurately. Moment magnitude, calculated straight from the physical rupture, doesn't have that ceiling.

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Why the Giants All Strike at Subduction Zones

Every earthquake above magnitude 8.6 in recorded history has occurred at a subduction zone — a place where one tectonic plate is forced down and under a neighboring plate, plunging back into the mantle. The reason is purely mechanical: only these enormous, gently sloping faults are physically large enough to store and release the colossal energy a magnitude 9 event requires.

Picture two sheets of sandpaper pressed together at a shallow angle, one sliding slowly beneath the other. At most points along that contact, friction locks the two surfaces together even as the plates keep grinding forward at a few centimeters per year, roughly the speed your fingernails grow. Stress accumulates at the locked patch for decades or centuries. When the friction finally fails, the entire locked section can rupture in a matter of minutes, releasing centuries of stored strain in one event.

The scale of these ruptures is difficult to grasp with everyday intuition. The 1960 Chile earthquake ruptured a fault roughly 1,000 kilometers (620 miles) long — about the driving distance from Los Angeles to Portland, Oregon, moving in a single event lasting minutes rather than the hours a road trip takes (USGS). The 2004 Sumatra–Andaman earthquake was even longer: its fault ruptured for more than 1,500 kilometers (930 miles), with the shaking itself lasting almost 10 minutes, an eternity for an earthquake where most events are over in under a minute (EARTH 107, Penn State).

No other type of fault on Earth can move that much rock in a single event. Strike-slip faults, like California's San Andreas, are steep and comparatively narrow, which caps how much fault area can rupture at once — that's part of why California's worst-case earthquakes top out well below magnitude 8.5. This geometric ceiling is exactly why the Pacific "Ring of Fire," the horseshoe-shaped chain of subduction zones ringing the Pacific Ocean, produces essentially every one of the planet's largest recorded quakes, from Chile and Alaska to Japan and Kamchatka.

What actually happens to the rock during rupture?

During rupture, the overriding plate that has been dragged downward for decades springs back upward and seaward, like a bent diving board released. In the 2004 Sumatra event, this thrust lifted sections of the seafloor by around 40 meters (130 feet) in places, and in the 1964 Alaska quake, some stretches of coastline rose by as much as 11.6 meters (38 feet) while other stretches sank by up to 2.4 meters (8 feet) (Britannica). That's not incremental geological drift measured over centuries; it's meters of permanent land movement in minutes.

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The Real Killer: Tsunamis

The greatest earthquakes are often deadliest not from the shaking itself but from the tsunamis they launch. When a subduction-zone fault slips, the sudden vertical displacement of the seafloor pushes an enormous column of ocean water upward all at once. That water doesn't stay stacked up — it collapses outward as a set of waves that can cross entire ocean basins at speeds comparable to a commercial jet aircraft, typically 500 to 800 kilometers per hour (310 to 500 miles per hour) in deep water.

The three deadliest events on the list illustrate just how far and how lethal this can reach:

• The 1960 Chile quake generated tsunami waves up to 25 meters (80 feet) high on the nearby coast, then sent the wave energy racing across the entire Pacific basin. It killed roughly 61 people in Hawaii and around 140 in Japan, more than 17,000 kilometers (10,500 miles) away, some 22 hours after the quake itself (USGS Earthquake List; WSSPC Tsunami Center).
• The 2004 Sumatra–Andaman quake produced the deadliest tsunami in recorded history. Waves exceeding 20 meters (65 feet) struck the coast and reached up to 3 kilometers (1.9 miles) inland in low-lying areas, ultimately killing more than 227,000 people across 14 countries and displacing 1.7 million more, with total economic losses estimated at $9.9 billion at the time (Britannica; Australian Disaster Resilience Knowledge Hub).
• The 1964 Alaska quake's tsunami reached local wave heights of up to 70 meters (230 feet) in enclosed fjords like Shoup Bay, and killed 131 people in total, most from the tsunami rather than the shaking (NCEI, NOAA; Dr. George Pararas-Carayannis).
• The 2011 Tōhoku quake's tsunami overtopped coastal sea walls that had been engineered for smaller events, and its floodwaters caused the meltdowns at the Fukushima Daiichi nuclear plant. More than 90 percent of the roughly 19,700 confirmed deaths from that disaster were caused by drowning in the tsunami, not by the earthquake's shaking (NCEI, NOAA; World Nuclear Association).

The 1960 Chile tsunami was, in fact, the first tsunami ever recorded by tide gauges across the entire globe, including instruments in the Atlantic and Indian Oceans — a wake-up call that directly accelerated the build-out of the Pacific Tsunami Warning Center's regional network in the years that followed (NOAA).

Why is the tsunami often deadlier than the earthquake itself?

Buildings can be engineered to survive strong shaking, and modern seismic codes in places like Japan do this well. Tsunamis, though, hit low-lying coastal populations with a wall of moving water carrying immense mass and momentum, often arriving with only minutes of warning in the near field. Unlike shaking, which stops within minutes, floodwater keeps advancing and doesn't discriminate between reinforced structures and open ground, which is why coastal death tolls from these events routinely dwarf inland ones.

This pattern, where the secondary hazard outkills the primary one, is a recurring theme across the deadliest natural disasters in history, where floods, famine, and tsunamis frequently account for more fatalities than the geological trigger event itself.

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Effects That Sound Like Fiction

The 1960 Chile earthquake's power produced effects that read like exaggeration but are documented, measured physical consequences of moving a slab of rock the size of a small country in a matter of minutes.

It set off free oscillations of the whole planet. Enough energy passed through the Earth that the entire globe rang like a struck bell, with these "free oscillations" — the planet's fundamental vibrational modes — detectable on seismometers for weeks after the initial rupture. This is the same physical principle that makes a bell hum after you stop striking it, just applied to a sphere 12,742 kilometers (7,918 miles) in diameter instead of a few centimeters of bronze.

It measurably changed the length of Earth's day. The 2011 Tōhoku earthquake, though weaker than Chile 1960, gives scientists a well-documented, precisely calculated example of this effect. NASA Jet Propulsion Laboratory geophysicist Richard Gross calculated that by shifting mass distribution closer to Earth's rotational axis, Tōhoku shortened the length of a day by about 1.8 microseconds, later refined to roughly 1.4 microseconds using an updated USGS model of the fault slip (NASA JPL; EarthSky). Because Chile 1960 released more than twice the energy of Tōhoku, its effect on Earth's rotation is understood to have been larger still, though it predates the precise satellite-based measurement systems used to calculate Tōhoku's effect.

The mechanism is the same one figure skaters use to spin faster: pull mass closer to your axis of rotation, and rotation speeds up, exactly the way a skater speeds up when they draw their arms in. A subduction earthquake does something similar on a planetary scale, shifting a slab of crust that used to sit farther from Earth's rotation axis to a position slightly closer to it.

It shifted Earth's figure axis. JPL's calculations for Tōhoku found that the quake also shifted Earth's "figure axis" — the axis around which the planet's mass is balanced, not the same as the north-south rotational axis — by about 17 centimeters (6.5 inches). This causes the planet to wobble very slightly differently as it spins, though it doesn't shift Earth's axis in space in any way a person would ever notice.

None of these are metaphors. They are measured, published consequences of moving a continent-scale slab of rock in minutes rather than millennia — the same order of physical extremity you see in the most extreme pressure conditions on Earth, where matter is subjected to forces that don't exist anywhere in ordinary human experience.

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Case Study: Valdivia, Chile, 1960 — the record that hasn't been broken since instruments existed

The Great Chilean earthquake struck on May 22, 1960, off the coast of the Biobío and Los Ríos regions of southern Chile. Its epicenter was near the city of Valdivia, and estimates of the rupture length range from about 500 to nearly 1,000 kilometers (310 to 620 miles) along the Chilean coast (National Geographic Education).

Official USGS-cited casualty figures for Chile itself range from 1,655 to as high as 5,700 depending on the study and how indirect deaths were counted, with roughly 2 million people left homeless across the affected region (USGS-cited list). The disaster was compounded within days by the eruption of the nearby Cordón Caulle volcano, itself apparently triggered by the stress changes from the earthquake, a reminder that these events rarely arrive in isolation.

What makes Valdivia scientifically distinct from every other quake on this list is the margin. At magnitude 9.5, it sits noticeably above magnitude 9.2 (Alaska, 1964) and magnitude 9.1 (Sumatra 2004 and Tōhoku 2011). Given the logarithmic energy relationship, that half-magnitude-unit gap between 9.5 and 9.1 corresponds to roughly two and a half times more energy released — meaning Chile's quake was not narrowly "the biggest," it was categorically in its own tier. In over 65 years of continuous global seismic monitoring since, no recorded event has come within half a magnitude unit of it.

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Case Study: The 1964 Alaska earthquake — America's largest, and a warning system's origin story

The Good Friday earthquake struck Prince William Sound, Alaska, on March 27, 1964, at a depth of about 25 kilometers (15.5 miles). At magnitude 9.2, it remains the largest earthquake ever recorded in United States history and the second-largest in the world (Britannica). Shaking lasted nearly five minutes, an extraordinarily long duration that alone caused significant damage in Anchorage, more than 120 kilometers (75 miles) from the epicenter.

Vertical land movement along the Alaskan coast was dramatic and permanent: some areas rose as much as 11.6 meters (38 feet), while other areas sank by up to 2.4 meters (8 feet), and much of the coastline shifted seaward by roughly 15 meters (50 feet). The subsequent tsunami killed most of the 131 total fatalities, with local wave run-ups reaching 70 meters (230 feet) in confined bays like Shoup Bay, among the highest tsunami run-up heights ever documented anywhere on Earth (NCEI, NOAA).

Because Alaska in 1964 was sparsely populated compared to today, the death toll stayed comparatively low for a quake of this magnitude. But the event permanently reshaped how the United States thinks about tsunami risk, feeding directly into the expansion of the Pacific Tsunami Warning Center's monitoring network, established after the 1960 Chile event and stress-tested by the 1964 Alaska disaster just four years later.

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Case Study: Sumatra–Andaman, 2004 — the earthquake that made the world watch a tsunami in real time

The Sumatra–Andaman earthquake struck on December 26, 2004, roughly 85 kilometers (53 miles) off the coast of northern Sumatra, Indonesia, at a depth of about 30 kilometers (19 miles). Its fault ruptured for more than 1,500 kilometers (930 miles) along the boundary between the Indian and Australian plates and the overriding Sunda plate, with the shaking itself lasting nearly 10 minutes, one of the longest-duration earthquakes ever recorded (EARTH 107, Penn State).

Slip along the fault reached about 15 meters (50 feet) in places, over a rupture area roughly the size of California. That thrust lifted parts of the seafloor by around 40 meters (130 feet), generating a tsunami with waves exceeding 20 meters (65 feet) at landfall that reached as far as 3 kilometers (1.9 miles) inland in flat coastal terrain.

Because no basin-wide tsunami warning system existed for the Indian Ocean at the time, unlike the Pacific, warnings that could theoretically have saved tens of thousands of lives in Sri Lanka, India, and Thailand — countries hit hours after Indonesia — never reached the people who needed them. The death toll exceeded 227,000 people across 14 countries, making it the deadliest tsunami in recorded history (Britannica). The disaster directly led to the creation of the Indian Ocean Tsunami Warning System, which came online in 2006.

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Case Study: Tōhoku, 2011 — the best-instrumented giant earthquake in history

The Tōhoku earthquake struck on March 11, 2011, in the Japan Trench off the coast of Honshu, with a magnitude between 9.0 and 9.1 depending on the model used. Because Japan operates one of the densest and most sophisticated seismic and GPS monitoring networks on Earth, this is the most precisely measured magnitude-9 earthquake in history, giving scientists like Richard Gross at NASA JPL the data needed to calculate its length-of-day and figure-axis effects with confidence rather than rough estimation.

The tsunami it generated overwhelmed coastal defenses engineered for smaller events and reached the Fukushima Daiichi Nuclear Power Station, where flooding disabled backup cooling systems and triggered meltdowns in three reactors, the worst nuclear accident since Chernobyl. Japan's National Police Agency has recorded roughly 15,900 confirmed deaths and over 2,500 people still listed as missing, with more than 90 percent of deaths attributed to drowning rather than building collapse (World Nuclear Association; NCEI, NOAA).

Tōhoku demonstrates something important: Japan's earthquake-resistant building codes, among the strictest in the world, meant that the shaking itself caused comparatively limited structural collapse relative to the magnitude. The catastrophe came almost entirely from the water that followed.

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Common Confusions and What People Get Wrong

"The biggest earthquake ever recorded" versus "the biggest earthquake ever." Every ranking on this page is bounded by the phrase "ever recorded," meaning since reliable, global instrumental seismology began in the early twentieth century. Geological evidence from paleoseismology — the study of ancient earthquake deposits preserved in sediment layers — suggests some prehistoric subduction earthquakes, including past ruptures on the Cascadia subduction zone off the U.S. Pacific Northwest, may have approached or matched these magnitudes, but without instruments running at the time, they can't be assigned a precise number.

Confusing magnitude with intensity. Magnitude is a single number describing the total energy released at the source. Intensity, often reported on the Modified Mercalli Intensity scale, describes how strongly the ground shook at a specific location, which depends heavily on distance from the epicenter, depth of the rupture, and local soil conditions. A magnitude 9 quake can register "violent" shaking near the epicenter and be barely perceptible 1,000 kilometers away.

Assuming higher magnitude always means more deaths. The 1960 Chile quake, the most powerful ever recorded, killed a small fraction of the people the smaller-magnitude 2004 Sumatra event did. Death toll depends far more on coastal population density, building codes, and whether an effective tsunami warning system existed than on the raw magnitude number.

Thinking these are once-in-history freak events. Subduction zones capable of producing magnitude 9 earthquakes exist today around much of the Pacific Rim, including off the coast of the U.S. Pacific Northwest (Cascadia), Alaska, Chile, and Japan. Seismologists consider several of these "seismic gaps" — segments overdue for their next major rupture based on historical recurrence intervals — active areas of ongoing research and monitoring, not settled history.

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The takeaway

The strongest earthquake ever recorded by instruments happened off the coast of Chile in 1960, and because the magnitude scale is logarithmic rather than linear, its 9.5 rating means it stands in a category by itself, not merely at the top of a close pack. Every giant earthquake on record shares the same origin, a subduction zone where one tectonic plate grinds beneath another over centuries before releasing that stored strain in minutes, and the tsunamis these ruptures generate have killed far more people than the shaking itself. The clearest lesson from Chile 1960, Alaska 1964, Sumatra 2004, and Tōhoku 2011 isn't that these events are freakish anomalies. It's that the same subduction zones that produced them are still active today, and the difference between a low death toll and a catastrophic one has consistently come down to warning systems and building codes, not the size of the earthquake itself.

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Frequently Asked Questions

Q: What is the strongest earthquake ever recorded? A: The 1960 Valdivia earthquake in Chile, at magnitude 9.5, the most powerful since seismographic instruments could reliably measure global quakes. It ruptured a fault estimated at 500 to 1,000 kilometers (310 to 620 miles) long, triggered a Pacific-wide tsunami, and released more energy than every other recorded earthquake of the 20th century combined.

Q: How much stronger is a magnitude 9 than a magnitude 8 earthquake? A: About 32 times more energy. The moment magnitude scale is logarithmic: each whole number represents roughly 10 times more ground-shaking amplitude and about 32 times (10^1.5) more energy released. Across two whole numbers, from 7 to 9, that compounds to roughly 1,000 times more energy, which is why a magnitude 9.5 like Chile 1960 sits so far above a "mere" 9.0.

Q: Why do the biggest earthquakes happen at subduction zones? A: Because only these large, gently sloping faults, where one tectonic plate dives beneath another, are physically big enough to store and release the amount of energy a magnitude 9 event requires. Stress builds for decades or centuries while the fault stays locked, then a vast section, sometimes over 1,000 kilometers long, ruptures at once. Nearly all the largest recorded quakes strike around the Pacific "Ring of Fire" for exactly this reason.

Q: Can an earthquake really change the length of a day? A: Yes, by a tiny but precisely calculated amount. NASA JPL geophysicist Richard Gross calculated that the 2011 Tōhoku earthquake shortened the length of a day by about 1.4 microseconds by shifting Earth's mass closer to its rotational axis, similar to how a spinning skater speeds up by pulling in their arms. The 1960 Chile quake, being more than twice as energetic, is understood to have had an even larger effect, though it predates the precise satellite measurements used for Tōhoku.

Q: Why are big earthquakes so deadly even far from the epicenter? A: Tsunamis. A subduction quake can thrust the seafloor upward by tens of meters, displacing an enormous volume of water that travels across entire ocean basins at speeds comparable to a jet aircraft. The 2004 Sumatra tsunami killed more than 227,000 people across 14 countries, many of them thousands of kilometers from the earthquake itself, which is why tsunamis are frequently deadlier than the ground shaking that causes them.

Q: What is the difference between the Richter scale and the moment magnitude scale? A: The Richter scale, developed in the 1930s, measures wave amplitude on a specific instrument and "saturates" above about magnitude 7, meaning it can't accurately distinguish an 8 from a 9.5. The moment magnitude scale, introduced by Hanks and Kanamori in 1979, is calculated directly from the physical properties of the rupture: fault area, slip distance, and rock rigidity. It has no such ceiling, which is why every quake on this list is measured in moment magnitude, not Richter.

Q: Has any earthquake before instruments existed possibly been larger than Chile 1960? A: Possibly, but it can't be proven with a specific number. Paleoseismology, the study of ancient earthquake deposits in coastal sediment layers, suggests some prehistoric subduction ruptures, including past events on North America's Cascadia subduction zone, may have approached similar magnitudes. Without instrumental records at the time, though, seismologists can only estimate a rough range, not assign a precise figure the way they can for events since the early 20th century.

Q: Could a magnitude 9+ earthquake happen again? A: Yes. Subduction zones capable of producing magnitude 9 earthquakes remain active today around large sections of the Pacific Rim, including Cascadia (U.S. Pacific Northwest), Alaska, Chile, and Japan. Seismologists actively study "seismic gaps," fault segments that are overdue for rupture based on historical recurrence patterns, and treat these regions as ongoing monitoring priorities rather than settled history.

Q: Why did the 2004 Sumatra tsunami kill so many more people than the 1960 Chile tsunami despite a lower magnitude? A: Primarily because no basin-wide tsunami warning system existed for the Indian Ocean in 2004, while the Pacific Tsunami Warning Center, established after the 1960 Chile disaster, was already operational for the Pacific basin. Densely populated, low-lying coastlines in Indonesia, Sri Lanka, India, and Thailand had no advance warning before waves arrived, whereas Pacific nations affected by the Chile tsunami had at least some monitoring infrastructure in place.

Q: What caused the Fukushima nuclear disaster during the 2011 Tōhoku earthquake? A: The earthquake itself did not critically damage the Fukushima Daiichi plant. The subsequent tsunami, which overtopped seawalls engineered for a smaller event, flooded the facility and disabled the backup diesel generators that powered the reactor cooling systems. Without cooling, three reactors overheated and experienced meltdowns, making it the worst nuclear accident since the 1986 Chernobyl disaster.

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Read next

• The Deadliest Natural Disasters in History
• The Biggest Explosions in History
• The Largest Volcanic Eruptions in History

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Sources

• United States Geological Survey (USGS) — 10 Largest Earthquakes Ever Recorded
• Hanks & Kanamori (1979), "A Moment Magnitude Scale," Journal of Geophysical Research
• NOAA NCEI — On This Day: 1960 Chilean Earthquake and Tsunami
• WSSPC Tsunami Center — 1960 Chile Tsunami
• Britannica — Alaska Earthquake of 1964
• NOAA NCEI — Great Alaska Earthquake
• Penn State EARTH 107 — The 2004 Sumatran Earthquake
• Britannica — Indian Ocean Tsunami of 2004
• NOAA NCEI — On This Day: 2011 Tohoku Earthquake and Tsunami
• World Nuclear Association — Fukushima Daiichi Accident
• NASA Jet Propulsion Laboratory — Japan Quake May Have Shortened Earth Days, Moved Axis
• EarthSky — Japanese Earthquake Shortened Earth's Day 1.4 Microseconds

Bottom line: The strongest quake ever recorded rang the whole planet like a bell and measurably nudged its rotation, and because magnitude is logarithmic, Chile 1960 still towers over every earthquake measured since.

Last verified: July 2026