seismology

When a magnitude 6.8 earthquake shook Olympia, Wash., in 2001, shop owner Jason Ward discovered that a sand-tracing pendulum had recorded the vibrations in the image above.

Seismologists say that the “flower” at the center reflects the higher-frequency waves that arrived first; the outer, larger-amplitude oscillations record the lower-frequency waves that arrived later.

“You never think about an earthquake as being artistic — it’s violent and destructive,” Norman MacLeod, president of Gaelic Wolf Consulting in Port Townsend, told ABC News. “But in the middle of all that chaos, this fine, delicate artwork was created.”

Source: http://www.futilitycloset.com/2012/11/16/the-earthquake-rose/

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Tōhoku Japanese Earthquake Sculpture by Luke Jerram

About the piece:

This sculpture was made to contemplate the 2011 Tōhoku earthquake and tsunami in Japan. To create the sculpture a seismogram of the earthquake, was rotated using computer aided design and then printed in 3 dimensions using rapid prototyping technology. The artwork measures 30cm x 20cm and represents 9 minutes of the earthquake.

Look for it soon at the Jerwood Space in London for a show called Terra. The show will also include his fantastic virus sculptures.

STEM Bunnies: Science, Technology, Engineering, and Mathethmatics

Science

"Science is a way of thinking much more than it is a body of knowledge." - Carl Sagan, astronomer

"The best scientist is open to experience and begins with romance - the idea that anything is possible." - Ray Bradbury, Author of Fahrenheit 451

Technology

"The most important and urgent problems of technology today are no longer the satisfcations of the primary needs or of archetypical wishes, but the reparation of the evils by the technology of yesteryear." - Dennis Gabor, Electrical Engineer and Physicist

"We made the buttons on the screen look so good you’ll want to lick them." - Steve Jobs, Chairman and CEO of Apple

Engineering

"I’m quite into the idea of engineering being beautiful." - Sean Booth

"Engineering is treated with disdain, on the whole. It’s considered to be rather boring and irrelevent, yet neither of those is true." - James Dyson, Industrialist and Inventer of the Bagless Vacuum Cleaner

Mathematics

"One of the most amazing things about mathematics is the people who do math aren’t usually interested in application, because mathematics itself is truly a beautiful art form." - Dania McKeller, Actor, Author, and Academic

"Somehow it’s OK for people to chuckle about not being good at math. Yet, if I said, ‘I never learned how to read,’ they’d say I was an illiterate dolt." - Neil deGrasse Tyson, Astrophysicist

STEM

“We live in a society exquisitely dependent on science and technology, in which hardly anyone knows anything about science and technology.”  - Carl Sagan, Astronomer

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The Most Dangerous City in the World

On the eastern edge of the Democratic Republic of Congo, the perilous Nyiragongo volcano towers 3470m over the city of Goma. The wildly erratic volcano is one of the most active on the planet, famous for the violent 200-metre-wide lava lake cradled in its vast summit crater, constantly emitting deadly gases and huge geysers of liquid rock. In 1977 and 2002, the volcano spewed deadly molten rock towards the million inhabitants of Goma, killing hundreds, forcing evacuations and destroying homes—but these were just small disturbances compared to what Nyiragongo is capable of unleashing. The volcano has an intricate ‘plumbing’ system like roots of a tree snaking deep underground, with vents not just at its summit but all around it, and so the threat to Goma is very immediate, and it has been dubbed ‘the most dangerous city in the world’ by researchers. The question is not if the volcano will erupt, but when. And yet, Nyiragongo is one of the least studied volcanoes in the world, because for the past twenty years, the Democratic Republic of Congo has experienced almost constant warfare. A deeper understanding of Nyiragongo must be gained in order to prevent a catastrophe, but serious research has only begun in the past few years. Until we can predict its activity, the question of when? will haunt scientists and seismologists alike, and will determine the fate of nearly one million people.

(Image Credit: Carsten Peter)

UC Berkeley’s Early Warning System Beat Napa Earthquake by 10 Seconds

Ten seconds before the San Francisco Bay Area started shaking early Sunday morning, an experimental system in a UC Berkeley lab sounded an alarm, counting down to the impending earthquake. The system works through an array of sensors near the fault line which calculate the severity of the quake and broadcast a warning.

It might not seem like much, but even a few seconds notice could allow utilities to shut off gas lines, elevators to let people off at the next floor, and trains to slow down. The USGS cites the benefits a warning could give to a doctor in the middle of performing surgery. In 2012, BART adopted an automatic braking system linked to the program, called Shake Alert.

Read more about UC Berkeley’s earthquake early warning system.

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MAJOR EARTHQUAKE TODAY

(CNN) — An 8.2-magnitude earthquake struck off the coast of northern Chile on Tuesday, generating a tsunami, authorities said.

The U.S. Geological Survey reported the quake, which hit at at 6:46 p.m. local time, was centered some 60 miles northwest of Iquique at a depth of 12.5 miles.

Chile’s National Emergency Office tweeted Tuesday night that it was asking everyone to evacuate the South American nation’s coast.  

A tsunami warning was in effect for Chile, Peru and Ecuador.

A tsunami watch was issued for Colombia, Panama and Costa Rica, according to the Pacific Tsunami Warning Center.

USGS National Earthquake Information Center

The April 1, 2014 M 8.2 earthquake in northern Chile occurred as the result of thrust faulting at shallow depths near the Chilean coast.

The location and mechanism of the earthquake are consistent with slip on the primary plate boundary interface, or megathrust, between the Nazca and South America plates. At the latitude of the earthquake, the Nazca plate subducts eastward beneath the South America plate at a rate of 65 mm/yr.

Subduction along the Peru-Chile Trench to the west of Chile has led to uplift of the Andes mountain range and has produced some of the largest earthquakes in the world, including the 2010 M 8.8 Maule earthquake in central Chile, and the largest earthquake on record, the 1960 M 9.5 earthquake in southern Chile.

NOAA Pacific Tsunami Warning Center

TSUNAMI INFORMATION STATEMENT NUMBER   3
NWS PACIFIC TSUNAMI WARNING CENTER EWA BEACH HI
235 PM HST TUE APR 01 2014

TO - CIVIL DEFENSE IN THE STATE OF HAWAII
SUBJECT - TSUNAMI INFORMATION STATEMENT

THIS STATEMENT IS FOR INFORMATION ONLY.
NO ACTION IS REQUIRED AT THIS TIME. HOWEVER… THE TSUNAMI THREAT TO HAWAII IS STILL BEING EVALUATED.

THE PACIFIC TSUNAMI WARNING CENTER HAS ISSUED AN EXPANDING REGIONAL TSUNAMI WARNING AND WATCH FOR PARTS OF THE PACIFIC  LOCATED CLOSER TO THE EARTHQUAKE. AN EVALUATION OF THE PACIFIC WIDE TSUNAMI THREAT IS UNDERWAY AND THERE IS A POSSIBILITY THAT HAWAII COULD BE ELEVATED TO A WATCH OR WARNING STATUS.

 IF TSUNAMI WAVES IMPACT HAWAII THEIR ESTIMATED EARLIEST ARRIVAL TIME IS   0324 AM HST WED 02 APR 2014

How Are Earthquakes Measured?

Thanks to the scale at which they take place, natural disasters can be challenging to measure. Consider earthquakes: you can’t ask how high an earthquake is, or quantify the weight of tectonic plates shifting against one another. What seismologists try to do instead is to measure the energy released by a quake, which you can learn all about at the Museum’s Nature’s Fury exhibit.

Aftermath of the San Francisco earthquake, 1906. © Library of Congress

Efforts to detect earthquakes stretch back thousands of years. In 132 CE, Chinese polymath Zhang Heng crafted what is thought to be the first seismic instrument, a bronze vase-shaped device with eight tubes, corresponding to direction points on a compass, protruding from it. When the vase detected an earthquake, the ball would drop from the appropriate tube into a container below, indicating the direction of the quake. Contemporary reports indicate this primitive seismoscope could detect quakes hundreds of miles away, though later attempts to replicate the device couldn’t reproduce this degree of accuracy.

Fast-forward to the 20th century. Most Americans are familiar with the Richter scale, which was developed by seismologist Charles Richter in 1935 at the California Institute of Technology. This scale is based on the largest shock wave recorded by a seismograph 100 km from the earthquake epicenter (the point on Earth’s surface directly above the rupture).

Gurlap CMG3T compact sesimometer, courtesy of Gurlap

Initially devised only to compare the strength of moderate quakes along the San Andreas fault in southern California, the Richter scale was eventually generalized to measure earthquakes all over the world. The Richter scale is logarithmic, with each step up the scale marking a tenfold increase in quake strength—a 4.0 quake on the Richter scale is, for instance, releases 10 times the energy of a 3.0 earthquake. The problem was that for large quakes—over 7.0 on the scale—the Richter scale was less reliable.

In 1979, as geologists developed more accurate techniques for measuring energy release, a new scale replaced the Richter: the moment magnitude, or MW scale, which seeks to measure the energy released by the earthquake. It’s also a logarithmic scale and comparable to Richter for small and medium quakes—a 5.0 on the Richter scale, for example, is also about a 5.0 MW quake—but better-suited to measuring large quakes.

No matter what scale is used, quakes are detected using devices called seismographs, which measure ground motion and produce images showing how these vibrations travel over time. The magnitude of a quake determines how it is classified by organizations such as the U.S. Geological Survey, from  “micro” quakes—the smallest that can be felt by humans—to “great” quakes, which can cause devastation over huge areas.

This post was originally published on the Museum blog

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TSUNAMI ANIMATION: NORTHEN CHLE, 1 APRIL 2014

  • PTWC’s near real-time animation for the tsunami from northern Chile on 1 April 2014 resulting from an offshore 8.2 magnitude earthquake in the region. The animation shows simulated tsunami wave propagation for 30 hours followed by an “energy map” showing the maximum open-ocean wave heights over that period and the forecasted tsunami run up heights on the coastlines.
  • Animación en tiempo casi real del PTWC para el tsunami en el norte de Chile el 01 de abril 2014 como resultado de un terremoto en alta mar 8.2 de magnitud en la región. La animación muestra la propagación de ondas de tsunami simulado durante 30 horas, seguido de un “mapa de la energía” que muestra las alturas máximas de olas de mar abierto durante ese período y la altura prevista de impacto en la costas del océano pacifico.

'Starquakes' Reveal Hidden Secrets Inside Stars

Starquakes in red giants — seismic shivers that can run all the way to the hearts of those stars — now reveal that their cores spin much faster than their surfaces, researchers find.

This discovery could shed light on how the otherwise mysterious interiors of stars evolve over time, scientists said.

Red giants represent the swollen fate that awaits stars such as our own sun as they begin to exhaust their hydrogen fuel. As they do so, their cores contract and their outer envelopes expand and cool.

Approximately 5 billion years from now, this process will force our sun to swell to more than 100 times its current size, transforming it into a red giant.

The shrinking of the hearts of these stars should make the cores whirl faster, just as spinning ice skaters turn faster if they pull their arms in. Still, until now, scientists only had indirect evidence of this occurring.

Now, by analyzing starquakes, researchers have discovered the centers of these stars apparently spin at least 10 times faster than their surfaces.

Starquakes

Stars experience violent quaking that generates sound waves. These ripples zip around inside the stars and cause tiny rhythmic variations in their brightness. By studying these changes, scientists can better understand stars’ interiors — an emerging scientific field known as asteroseismology.

Using NASA’s Kepler spacecraft and ground-based telescopes, researchers observed three red giants for more than 500 days. Vibration-linked variations in their brightness showed how fast their cores were spinning.

Seeing with Seismic Waves

Earth is a rocky terrestrial planet, layered like a spherical, incredibly hot, completely unpalatable cake (so, not really like a cake at all). The outermost layer is the crust, followed by the molten mantle, then the metallic core, which is made mainly of iron and nickel but split into two parts: the outer core is churning liquid, and the inner core is a dense, rotating solid ball.

The deeper we go down, the hotter and more pressurised it becomes. The deepest hole humans have every drilled is only 12 kilometres down, not even deep enough to hit the mantle. So how do we know the structure and composition of the planet?

Our knowledge mainly comes from seismology, which allows us to study the planet’s interior based on how seismic waves travel through it. Seismic waves are produced by earthquakes, and they cause rock to either compress or to vibrate up and down. There are two types: P and S waves.

  1. P waves cause matter to move in a horizontal motion, compressing and stretching it like a spring. Sound waves are P waves, compressing and stretching the air in order to travel. These types of waves are much faster than S waves, and can travel through both solids and liquids.
  2. S waves cause matter to move up and down or side to wide, like the waves that travel up and down a jolted rope. They cause the most damage when earthquakes occur, as they physically displace the earth much more violently, even though they’re slower than P waves. However, they can’t travel through liquids.

(Image Credit)

The speed, size, and direction of these waves change depending on the density, composition, and temperature of the material they pass through. The fact that S waves can’t travel through liquid, for example, is vital to our knowledge of Earth’s interior. When an earthquake occurs in the crust, S and P waves are not only felt on the surface, but they also shoot down right through the Earth and can be detected on other parts of the planet. When seismologists measure these earthquake signatures around the world, they see a “shadow zones” where no waves have made it through. The key to this lies in the abrupt differences between the layers of the Earth.

Since S waves cannot travel through liquid, they can’t pass from the mantle and into the liquid outer core. Instead, they reflect off at an angle, leaving a huge shadow zone on the opposite side of the earth.  Meanwhile, P waves (which can travel through liquid) are able to pass through the core and emerge on the other side. Because of the way they bend as they pass through different mediums (from the dense core to the less dense mantle), they also create two, smaller shadow zones.

(Image Credit)

From this information about how waves reflect and refract, we’ve deduced the four main layers of our planet.

The cool thing is, these principles aren’t limited to the study of Earth’s interior. Similar instruments can be used on the surface of any solid planet—Apollo astronauts actually left seismometers on the Moon. The Moon isn’t broken into plates like the Earth, which collide and slip to cause earthquakes, so moonquakes are instead caused by tidal deformation. The Viking 2 lander attempted to use a seismometer on Mars, but the Martian winds prevented it from detecting any quakes. But studying seismology on Mars could help us understand fundamental questions about the planet’s geology, such as why its magnetic field decreased, and why it doesn’t have geological features similar to Earth’s, which could tell us more about the evolution of terrestrial planets.

by renowned seismologist Susan Hough:

  1. Animals sense impending earthquakes: "Every pet owner understands that, say, cats and dogs sometimes behave strangely for no apparent reason; that’s what cats and dogs do. And if an earthquake had not subsequently struck, you can bet we would not be talking about strange animal behavior this week — because we wouldn’t have noticed anything out of the ordinary."
  2. The frequency of large-scale earthquakes has spiked: "The number of earthquakes greater than magnitude 7.0 has been somewhat high in recent years but well within the range throughout the 20th century."
  3. Small earthquakes are helpful because they release pressure and prevent larger ones: "For each unit increase in magnitude (i.e., going from 5.5 to 6.5), the energy released rises by a factor of about 30. (…) If enough stress has built up on a fault to generate a magnitude-7.0 earthquake, say, it would thus take about 1000 earthquakes with a magnitude of 5.0 to release the equivalent energy. The Earth doesn’t work that way. (…) If there is significant strain energy to be released, it must be released in large earthquakes."
  4. "Don’t worry, it was just an aftershock.": "The implication is that an aftershock is somehow a less worrisome event. Yet, as far as we understand, an aftershock of a certain magnitude is no different from an independent temblor of a similar magnitude. The shaking and rupture are the same; the energy released is the same. And aftershocks can be more damaging than larger "mainshocks" if they strike closer to population centers."
  5. Earthquakes are a West Coast problem: "As millions of people on the East Coast were just reminded, less active does not mean inactive. By the end of the 19th century, two of the most notable temblors in the United States were the 1886 quake in Charleston, S.C., and a sequence of large events centered near the boot-heel along the New Madrid Fault of Missouri in 1811-1812. We don’t know exactly when or where the next Big One will hit the United States, but the central and eastern United States will inevitably experience large quakes in the future. (…) You have been warned."
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Seattle’s Seismic Stadium

 The state of Washington sits above a major earthquake-generating fault, the Cascadia subduction zone, where the Juan de Fuca plate sinks beneath North American. Consequently, the city is well covered with instruments capable of detecting even small seismic signals.

In 2011, during a football game by the Seattle Seahawks, Marshawn Lynch, the running back for the Seahawks, scored a touchdown on an impressive play, causing the stadium crowd to respond with such intense applause and jumping up and down that it shook the station. Those vibrations were actually measured by a seismic station a block away and equivalent in energy to about a magnitude 1 earthquake. The signal became nicknamed the “beast quake” after Lynch’s nickname.

This seismic station has measured a few similar events since then during Seahawks games, but now local geologists have decided to push this measurement forward.

Keep reading

Before A Volcano Erupts Violently: The Warning Signs

Volcanoes prone to explosive eruptions exist all over the world, but the warning signs are not well understood. Now, in a new study, a group of scientists including a senior author from Yale identifies the key signals of imminent eruption.

Violent volcanoes exist in areas near oceanic trenches where tectonic plates are sinking into the mantle. The plates drag down water which then facilitates melting in the hot mantle — and drives eruption at the surface. Some examples of these volcanoes include Mt. St. Helens and Mt. Rainier in the United States, Krakatau in Indonesia, Soufrière Hills in Montserrat, and Mt. Pelée on Martinique. Some are famous for historical catastrophes, such as the one on Mt. Pelée in 1902, which killed 30,000 people in the city of St. Pierre.

Volcanological observatories measure activity building up to an eruption — known as precursors — in order to monitor volcanic activity. These destructive volcanoes tend to shake or undergo tremor for hours or minutes before an eruption. But even before tremors, they also can undergo regular, repeated, slow oscillations in ground swelling and collapse, as well as gas release. These oscillations have cycles lasting several hours to a day, and the cycles repeat again and again for many days. Monitoring such long-term activity is vital to understanding whether an eruption is imminent, according to the researchers.

The authors propose that these long, slow oscillations are due to magma gas waves rising up inside the volcanic conduit — the central “chimney” through which magma rises before an eruption. If a layer of magma in the conduit gets particularly bubbly, it will rise more rapidly and travel as a gas-rich pulse or wave. If the pulse is big enough, the gas will expand as it rises, and the pulse will grow. If it’s too big, it will just leak out as it expands, so the pulse won’t grow as well. If it’s too small, the weight of the magma will squeeze the gas and make the pulse shrink and decay.

Therefore, gas pulses need to be just the right size, or waves have to have the right length, in order to survive on their way to the surface, and cause oscillations in ground swelling and gas release. The authors’ model predicting the time length of these cycles matches observations very closely.

Senior author David Bercovici, professor of geophysics at Yale University, said, “These slow magma waves are effectively selected by the magma column and are quite possibly the cause for these volcanic cycles and eruption precursors.”

Lead author is Chloé Michaut of Institut de Physique du Globe de Paris and former postdoctoral student at Yale, under Bercovici; other senior authors are Yanick Ricard of Université Lyon and R. Steven J. Sparks of University of Bristol.

This study was supported by Campus Spatial Paris Diderot and European Research Council Advanced Grant VOLDIES number 228064. The paper appears online in Nature Geoscience.

Source: yaleuniversity; YaleNews

What Direction Does Earth’s Center Spin? New Insights Solve 300-Year-Old Problem

Sep. 16, 2013 — Scientists at the University of Leeds have solved a 300-year-old riddle about which direction the centre of Earth spins.

Earth’s inner core, made up of solid iron, ‘superrotates’ in an eastward direction — meaning it spins faster than the rest of the planet — while the outer core, comprising mainly molten iron, spins westwards at a slower pace.

Continue Reading

A first today a KNS, a nick name to replace an eponym that is just about unprounounceable!  Today is the birthday of Andrija Mohorovičić, born on the 23rd of January 1857 (died 18 December 1936) Croatian meteorologist and seismologist who gave his unpronounceable (well, outside of Croatia) name to the boundary layer between the Earth’s crust and mantle.  In October of 1909 there was an earthquake just south of Zagreb.  A number of newly installed seismographs recorded the event and careful analysis led Mohorovičić to theorize that the earth was made up of distinct layers from the inner core to the outer crust, each of which propagated the seismic waves differently.  The discontinuity between the Earth’s crust and mantle was named after him, although since so few people (including me) can pronounce his name correctly, the Mohorovičić discontinuity is often referred to as the Moho discontinuity.  

Illustration ”Refraction of P-wave” by Brews ohare - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Refraction_of_P-wave.PNG#mediaviewer/File:Refraction_of_P-wave.PNG

Reading a seismogram

This is the actual seismogram recorded by a seismometer during a magnitude 5.0 earthquake on Jan Mayen island in 1995. There’s a lot of information in a graph like this if you know how to read it.

A classic seismogram is made by a pen held by a weight in a fixed position on top of a spinning roll of paper. During a quake, the inertia of the weight keeps the pen from moving, while the paper drum moves due to the waves. The pen then marks the drum as it moves back and forth. Modern instruments detect these waves electronically, but the principle is the same.

In this plot, time moves from left to right; the left side starts and the right side finishes. 3 different features stand out. The first hint of the quake is a small pulse of energy that decays away with some fine structure to it. Then, there’s a second pulse of energy, slightly less intense than the first. Just after this second pulse is when the biggest, most intense shaking starts.

This is the classic sequence of waves created in an earthquake. The fastest moving waves are called p-waves, a pressure wave moving through the earth. The next to arrive is an s-wave, a shear wave also moving through the earth. Finally, the largest pulse of energy arrives in the form of surface waves known as Rayleigh and Love waves. The surface waves are where the largest ground motions take place and when most of the damage is done. They also have a lower frequency than the p and s waves, meaning that the wave arrivals become more spread out.

The time between waves arriving at a seismic station depends on how far the station is from the quake. The farther away the station is, the bigger the difference in arrival times. The difference between the p wave arrival and surface wave arrivals can be as little as a fraction of a second for earthquakes very nearby and as long as tens of minutes for earthquakes far away. 

Each wave bounces and refracts off slightly different regions within the earth, leading to the complex structure in each portion. That complexity can be used by computers as a way of measuring actual differences inside the Earth. 

-JBB

Image credit: 
https://www.flickr.com/photos/rockbandit/309794495

Read more:
http://www.geo.mtu.edu/UPSeis/reading.html
http://tinyurl.com/o74xor4

Carbon Cycle Reaches Earth's Lower Mantle

The carbon cycle, upon which most living things depend, reaches much deeper into the Earth than generally supposed — all the way to the lower mantle, researchers report. A new study describes a set of rare, “superdeep” diamonds from the Juina kimberlite field in Brazil. The carbon in these diamonds appears to have been deposited within ocean crust at the seafloor. The crust then sank into the lower mantle, where the diamonds formed, the study suggests.

Read more, and listen to a podcast, about this research from the 16 September issue of Science here.

[Click the image for caption information.]

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