October 17 – Play Ball!

Today’s factismal: The first earthquake to be shown live on television happened in 1989.

You may have heard that there is a 72% chance that there will be a large earthquake near San Francisco sometime in the next thirty years. And that there is an  85% chance of a large earthquake on the San Andreas fault sometime in the next ten years. Experts think that it could cause as many as 1,800 deaths and as much as $200 billion in damage. But how can we know how much damage an earthquake will do? Simple – we know because we saw one happen, live on TV.

It was a balmy October evening in San Francisco. The Giants were competing with the Oakland A’s for the pennant, and the two teams were warming up in preparation for game three. As the television sports casters searched for something to add a little local color to the broadcast, they were given the greatest exclusive in history: an earthquake struck the area. And not some piddly little 4.0; this was a 6.9 Mb earthquake! As the anchors tried to describe what was happening, the world saw buildings shake, highways fall, and homes crumble into rubble.

A section of the collapsed highway (Image courtesy USGS)

A section of the collapsed highway
(Image courtesy USGS)

Amazingly, there were only 63 people killed in the earthquake (the 1905 temblor was about 30 times stronger and killed 3,000 people). Most of these happened in Oakland where a double-decker highway collapsed on itself. Interestingly, many credit the baseball game for the low fatality count. Because many people had left work early in order to watch the game, the highways were relatively uncrowded which meant that fewer people were hurt.

California is almost certain to have another large earthquake in the next three decades (Image courtesy SCEC)

California is almost certain to have another large earthquake in the next three decades
(Image courtesy SCEC)

But what is even more amazing is that the danger isn’t over. There is a 99.7% chance that some part of California will have another earthquake at least as powerful as this one in the next thirty years. So we know when the next big on will happen (soon); what we don’t know is where. And that’s where you can help. The USGS and Stanford University are developing a new type of distributed seismometer that uses the accelerometers in tablets, smartphones, and computers to provide more complete coverage of earthquakes; the data that this Quake Catcher Network gathers will then help them to narrow down when we can expect the next big one. If you’d like to take part, head over to:
http://qcn.stanford.edu/

August 24 – Tembling In Fear

Today’s factismal: An earthquake is called a temblor by the folks who study them.

The past 24 hours has been very interesting. In that time we’ve seen a Mb 6.8 earthquake in Burma, a Mb 6.2 temblor in Italy, and a Mb 6.0 event in Indonesia.

A comparison of the energy released by the big earthquakes we've had in the past day

A comparison of the energy released by the big earthquakes we’ve had in the past day

Though we still don’t know what the damage from these events will be, most experts expect it to be a few hundred dead in each case because the areas that were affected are mostly un-reinforced masonry buildings. that do not hold up well in an earthquake. Now, the typical lay reader is probably thinking “I should donate to the relief funds” and the typical lay reader would be right. Getting supplies and shelter to those in the disaster areas will definitely help more people survive. But the typical lay reader is probably also thinking “Gosh, three biggies in one day – there has to be something going on” and the typical lay reader would be wrong.

The past week's temblors (Image courtesy USGS)

The past days’s large temblors
(Image courtesy USGS)

The typical lay reader is wrong because there are earthquakes every day. Lots of them. On a typical day, there are about 4,000 earthquakes. Now most of those events are very small; they tend to be Mb 1 or Mb 2. But every year there are 134 or so events with a magnitude between 6 and 7. So on average we would expect to see an earthquake this large about once every three days. And since earthquakes happen at random, the odds of seeing three events in any given 24 hour period are not that bad – about 1 in 27. In other words, we should expect to have a replay of today’s events about once a month or so. Fortunately, most of the Earth is empty ocean so most of those replays take place far, far away from any people.

One year of earthquakes across the world. (Image courtesy the USGS)

One year of earthquakes across the world. (Image courtesy the USGS)

We get earthquakes because the Earth is hot inside. That heat creates motion in the mantle that geology wonks call convection. And the motion of the mantle drives motion of the Earth’s crust, breaking it into large rigid sections called plates. As the plates collide to form mountain ranges or scrape alongside in transform zones, they release energy as earthquakes. For Burma, the plates that are colliding are the India plate and the Eurasian plate and the mountains that are being built are the Himalayas. For Italy, the plates that are colliding are the Nubia plate and the European plate and the mountains that are being built are the Apennines. And for Indonesia, the plates that are colliding are the Australia plate and the India plate and the mountains that are being built are Indonesia. And though the temblors cause a lot of damage and deaths they also give us a chance to learn more about how to make the next one less dangerous.

The different layers of the Earth. Only the outer core is molten; everything else s solid!

The different layers of the Earth. Only the outer core is molten; everything else is solid!

You see, after each earthquake, people who felt it have gone to the Did You Feel It? page and told the USGS what they felt. That helped the geophysicists to determine which parts of the world are most susceptible to earthquake damage which tells  first responders where we need to improve building codes and emergency response.

The results of Did You Feel It? for the past decade (Image courtesy USGS)

The results of Did You Feel It? for the past decade
(Image courtesy USGS)

If you’d like to help, participating is easy. The next time you feel an earthquake, go over to Did You Feel It? and let them know what you felt. Then sit back and enjoy the knowledge that you’ve just helped make us all a little bit safer.

April 17 – Right In The Middle

Today’s factismal: The M 7.8 temblor in Ecuador is only one of 4,000 earthquakes that happened today.

You may remember that back in March I wrote that we would probably only see one or two M 7.8 earthquakes this year. The one on March 2 was the first. And yesterday, we have the second in Ecuador. That M 7.8 temblor (temblor is what seismologists call an earthquake) happened at 6:58 PM, killing 233 people and devastating wide swaths of the country. It was the strongest event in the area in the past thirty years and the seventh great earthquake (an event with magnitude greater than M 7) in Ecuador since 1900. This earthquake released the same amount of energy as 504 Hiroshima bombs; that’s enough energy to power a typical household for 332,871 years or a hurricane for 53 seconds. That energy did enormous damage to the area, mostly because the buildings there are mainly built of brick and masonry neither of which stand up well to shaking. But the temblor was actually not that strong as earthquakes go. In the past decade alone, there have been twenty events stronger than this one (and six that were just as strong).

The area affected by the M 7.8 event (epicenter marked by a star) (Image courtesy USGS)

The area affected by the M 7.8 event (epicenter marked by a star)
(Image courtesy USGS)

Since then, there have been 10 aftershocks recorded, with magnitudes ranging from 5.8 to 4.5. In practical terms, the main event released about 100 times more energy than the biggest aftershock and about 2,000 times more energy than the smallest. Over the next few weeks, we can expect to see upward of 100 more aftershocks; the strength should gradually decline to about M2 – but we can’t rule out the possibility of an exceptional aftershock with a magnitude larger than the original earthquake.

There are a lot more small earthquakes, but the big ones release a lot more energy!

There are a lot more small earthquakes, but the big ones release a lot more energy!

As astonishing as it may be to folks who don’t study earthquakes, the Ecuador event wasn’t the only temblor yesterday; indeed, there are about 4,000 events every day! That adds up to  nearly 30,000 earthquakes each week and nearly 1,500,000 earthquakes across the globe every year. But don’t worry. It isn’t unusual. It is actually all part of how planets work.

One year of earthquakes across the world. (Image courtesy the USGS)

One year of earthquakes across the world. (Image courtesy the USGS)

We get earthquakes because the Earth is hot inside. That heat creates convection in the mantle. And the motion of the mantle drives motion of the Earth’s crust, breaking it into large rigid sections called plates. As the plates collide to form mountain ranges or scrape alongside in transform zones, they release energy as earthquakes. For Ecuador, the plates that are colliding are the Nazca plate and the South American plate. And the mountains that are being built are the Andes. Unfortunately, the earthquakes that those colliding plates create cause lots of damage.

The different layers of the Earth. Only the outer core is molten; everything else s solid!

The different layers of the Earth. Only the outer core is molten; everything else is solid!

Lots and lots of damage. Not just buildings, but lives. This event killed at least 233 people and injured many more. So this time, I’m not going to ask you to do citizen science. Instead, I’m going to ask you to do something that will help the people of Ecuador. Please give to the World Help fund (here’s their rating on Charity Navigator). The money you give will go to help those hurt by natural disasters like this to restart their lives and rebuild their homes. To learn more, go to:
http://www.worldhelp.net/

March 2 – Boom Shake-A-Lotta!

Today’s factismal: The Earth may have had the strongest earthquake for 2016.

One of the most amazing things about the Earth is something that very few people outside of geologists think about: the Earth has earthquakes. A lot of earthquakes. And one reason that earthquakes are amazing is what they can tell us about the inside of the Earth. When earthquakes travel through the Earth, they are changed by the various layers in the Earth. Using a technique similar to a CAT scan (indeed, the medicos stole the idea from the geophysicists), we can learn things such as where old plates go to die and where water is stored in the mantle.

This look into the Earth's interior is thanks to earthquakes (Image courtesy USGS)

This look into the Earth’s interior is thanks to earthquakes
(Image courtesy USGS)

Another reason that earthquakes are amazing is because we can say so much for sure about them. For example, we know that the largest earthquake that we could have is a magnitude 9.5; anything larger than that would require a fault that is simply too long to exist. And we know that on average, we get two magnitude 7.8 (or larger) earthquakes each year which means that today’s Mb 7.8 temblor in Indonesia is probably the largest earthquake we’ll have all year.  We even know where we’ll have earthquakes and what sort of damage they’ll do, thanks to research done by citizen scientists like you.

This hazard map was created using data from citizen scientists (Image courtesy USGS)

This hazard map was created using data from citizen scientists
(Image courtesy USGS)

You see, after each earthquake, people who felt it have gone to the Did You Feel It? page and told the USGS what they felt. That helped the geophysicists to determine which parts of the USA (and elsewhere) were most susceptible to earthquake damage which tells our politicians which parts of the USA need to improve their building codes and emergency response.

The results of Did You Feel It? for the past decade (Image courtesy USGS)

The results of Did You Feel It? for the past decade
(Image courtesy USGS)

If you’d like to help, participating is easy. The next time you feel an earthquake, go over to Did You Feel It? and let them know what you felt. Then sit back and enjoy the knowledge that you’ve just helped make us all a little bit safer.

July 12 – Crack Around The World

An earthquake fossil, also known as a fault scarp (My camera)

An earthquake fossil, also known as a fault scarp
(My camera)

This is a fossil of an earthquake. It is a place where the forces on our plates caused one to split apart and move, creating a M 7.5 temblor beside  Hebgen Lake near Yellowstone National Park. The 1959 earthquake did almost $11 million in damage (about $90 million in 2015 money); worse, it triggered a landslide and killed 28 people. Today, about all that remains is this fault scarp.

The amazing thing about the scarp is that it shows how many mountains form, one earthquake at a time. Each temblor creates a small uplift. And hundreds of thousands of these small uplifts end up in mountains like the Rockies and Appalachians.

June 30 – Whose Fault Is It?

Today’s factismal: The Cascadia fault stretches more than 600 miles from Canada to California.

Anything you want to see in Seattle is either uphill or downhill; there are no flat parts to the city. That’s because the entire area is being squeezed together by the Juan de Fuca and North American plates. That collision has created the vast Olympic and Cascade mountain ranges (and volcanoes such as Mt. St Helens, Mt. Hood, and Mt. Rainier); the hills of Seattle are just the little foothills before the big mountains. The subduction zone also creates lots and lots of earthquakes. On average, Seattle has a magnitude 7 earthquake about once every fifty years; the last one was in 1965. Even better, the Cascadia fault is expected to create a magnitude 9 temblor every 400 years or so; the last one was in 1700.

Thnderbird figures in many of the local legends about earthquakes (My camera)

Thnderbird figures in many of the local legends about earthquakes
(My camera)

But what is the Cascadia fault? It is where the two plates meet. This 620 mile long intersection runs from Vancouver down to Cape Mendocino and stretches more than 40 miles across. Because the fault is so large and because it typically releases the stored energy all at once, it is sometimes called the “Cascadia megathrust”. Call it what you will, the amount of energy and damage that this thrust can release is simply astounding. A typical megathrust earthquake releases the same amount of energy that the USA uses in a week; put another way, it has the same power as 32,000 atomic bombs! (But it pales before a hurricane which would take just one hour to release the same amount of energy.) The last megathrust earthquake created a tsunami that raced across the Pacific Ocean and destroyed much of the island of Honshu; the temblor also created a landslide that is known in local legends as “the Bridge Of The Gods”.

The giant whale on the back fought Thunderbird and created the mountains and lakes by a series of earthquakes (My camera)

The giant whale on the back fought Thunderbird and created the mountains and lakes by a series of earthquakes
(My camera)

The amazing thing about the earthquake is that we know so much about it. And that is mainly because people talked about it when it happened and the events turned into legends that archeoseismologists could study. Today, we don’t need to wait for the legend to be born to learn about earthquakes. All you have to do is tweet! If you have a Twitter account and feel an earthquake or landslide, please send a tweet and mark it @USGSTed. To learn more, flit over to:
http://gallery.usgs.gov/audios/326#.VYg6t3JFCRs

May 5 – Whole Lot A Shakin’ Goin’ On

Today’s Factismal: There were nearly 4,000 earthquakes today.

There was just a Mw 7.5 earthquake off of Papua New Guinea today. And there was a Mw 7.8 temblor in Nepal last week. And they aren’t alone; over the past week, there were nearly 30,000 earthquakes. But don’t worry. There were that many earthquakes the week before, too. And there will be that many next week as well. The fact is that every day there are 4,000 earthquakes and every year there are nearly one and a half million earthquakes across the globe.

One year of earthquakes across the world. (Image courtesy the USGS)

One year of earthquakes across the world. (Image courtesy the USGS)

These earthquakes happen because the Earth is very slowly cooling down. Radioactive decay in the mantle (the thick solid section between the liquid outer core and the crust) and solidification of the outer core create heat inside the Earth. That heat, plus a little “fossil heat” from the Earth’s formation, creates convection in the mantle. And the motion of the mantle drives motion of the Earth’s crust, breaking it into large rigid sections called plates. As the plates collide to form mountain ranges or scrape alongside in transform zones, they release energy as earthquakes.

The different layers of the Earth. Only the outer core is molten; everything else s solid!

The different layers of the Earth. Only the outer core is molten; everything else is solid!

And what a lot of energy they release! A magnitude 2.5 earthquake will give off enough energy to power a home for 14 hours, and there are nearly 1,300,000 earthquakes that large every year. Even better, the energy goes up much faster than the magnitude. A magnitude 4 earthquake gives off enough energy to power a home for 1.6 years. Fortunately, the number of earthquakes also decreases faster than the magnitude; there are only about 13,000 magnitude 4 earthquakes every year.

There are a lot more small earthquakes, but the big ones release a lot more energy!

There are a lot more small earthquakes, but the big ones release a lot more energy!

And that relationship between energy and magnitude is why we can’t prevent a large earthquake by triggering a lot of small ones. It takes about 33 magnitude 7 earthquakes to release the same energy as one magnitude 8. So let’s suppose that you live in a place where you get a magnitude 8 about once every hundred years. You’d need to have a magnitude 7 every three years to release the strain. Or you could do it with a magnitude 6 every month. Or a magnitude 5 every day. Or a magnitude 4 every 45 minutes. Or a magnitude 3 every minute. Obviously, this is not a good idea.

What is a good idea is keeping up with the most recent earthquakes using either the Rapid Earthquake Viewer or the USGS Earthquake Monitor. And please contribute to science by telling the USGS if you felt the earth move!
http://earthquake.usgs.gov/earthquakes/dyfi/