Tag Archives: seismometer

Stunning animation shows how Marsquakes look like

The Earth has lots of earthquakes, but it’s not the only place with temblors. While Martian quakes are much smaller in intensity, they do exist — here’s how the seismic waves propagate through the planet:

Seismic waves from a marsquake as they move through different layers of the Martian interior. Credits: NASA/JPL-Caltech/ETH Zurich/Van Driel

Seeing the inside

When NASA sent astronauts to the moon in the Apollo 11 mission, they also had them deploy scientific instruments — including seismometers. But it took a couple more decades until the agency’s InSight lander brought the first seismometer to Mars in late 2018. Called the Seismic Experiment for Interior Structure (SEIS), the seismometer made history in April 2019, when it detected the first marsquake.

The mission is led by researchers at ETH Zurich in Switzerland who monitor and analyze the data. Because Mars doesn’t have active plate tectonics, it also has much fewer (and less intense) earthquakes. These temblors pose no realistic risk whatsoever — the purpose of the seismometer is to help researchers better understand the inside of the planet.

InSight’s seismometer has a cozy shelter on Mars. Credits: NASA.

Much of what we know about Earth’s internal structure also comes from seismology. When an earthquake occurs, it spreads out energy in the form of seismic waves. There are different types of waves which propagate differently through the Earth’s inside. By calculating the time of arrival between different types of waves, their amplitude, and several other parameters, seismologists make certain deductions about the Earth’s structure.

In a way, it’s a bit like how an ultrasound reading can reveal a baby inside a mother’s womb, except the scale and accuracy of the procedures is very different. Ultrasounds and seismic waves are both acoustic waves and they get similarly reflected and refracted. But researchers didn’t stop here.

Feeling a marsquake

Researchers at ETH took things even further: they wanted to see how a marsquake feels, compared to one on Earth or on the moon.

Of course, since the marsquake is much weaker than its earthly equivalent, the signal is also weaker. The team had to amplify the marsquake signals by a factor of 10 million in order to make the barely-perceptible tremors comparable to earthquakes. Moonquakes were similarly amplified.

The reason why quakes on different types of planets can feel differently is that they are affected by the material the waves pass through. We’re still in the very early days of studying marsquakes but so far at least, the results are encouraging.

The 2020 Mars Rover will also feature an instrument that will help researchers “see” beneath the Martian surface. The ground penetrating radar will use electromagnetic waves to create a high-resolution visualization of a Martian subsurface, at depths of up to 10 meters.

Mobile US seismic array maps American mantle

A laudable, ambitious initiative is nearing fruition: the US$90-million Transportable Array, a moveable grid of seismometers that blankets America.

Since 2004, the set of 400 seismometers, loaded on trucks, have gradually marched, from the Pacific coast across the Rocky Mountains and the Great Plains and is finally reaching the eastern coastline. Whenever they arrive at the specified location, scientists dig holes and bury instruments in plastic cases. The project’s purpose is to establishe the best picture yet of the mantle beneath the North American continent.

earthscope2

Source: IRIS.

Reaching a few hundred kilometers beneath the surface, the array analyzes how natural waves from earthquakes move in the mantle and the crust, painting the most accurate picture so far. The array works similar to a CT scan – moving across the surface and gathering information from more and more points.

“As the array has moved, the whole picture of what’s under North America has gotten much sharper,” says Andy Frassetto, a seismologist at the Incorporated Research Institutions for Seismology (IRIS) in Washington DC, which operates the stations.

Having almost finished their work in 48 states, they are now heading over to Alaska, where the toughest challenge awaits. The Transportable Array, along with other permanent and temporary seismic stations, is one of three cornerstones making up the larger EarthScope initiative. EarthScope is an earth science program using geological and geophysical techniques to explore the structure and evolution of the North American continent and to understand the processes controlling earthquakes and volcanoes. The EarthScope initiative has three components – the seismometers are just the first one. The second one is a set of GPS that measure tiny movements in the Earth’s crust, and the third one is a 3.2-kilometre-deep hole drilled into California’s San Andreas fault – but this step experienced a big setback when instruments lowered down the hole stopped working after just days for an unknown reason. But the first two initiatives more than made up for that:

“We’ve learned a lot more by integrating things together than we would have by doing them separately,” says Robert Smith, a geophysicist at the University of Utah in Salt Lake City, and an early leader of EarthScope.

Source: IRIS.

Source: IRIS.

Researchers are now eagerly waiting for the equipment to arrive in Alaska, which will provide some of the most valuable data from all the country. Alaska’s geology is interesting to say the least, with the the Pacific crustal plate slamming into and diving under the continent. But even with this spectacular tectonic development, little has be done to improve our understanding of the area – in part because the state is so big and it costs a lot to probe all of it, and partially because of the rough conditions.

“We have sort of a ‘zeroth’ order of understanding,” says Rick Saltus, a USGS geophysicist in Denver. Now, he says,“we’ll get the first order”.