From Horizon The EU Research and Innovation Magazine : “What happens below Earth’s surface when the most powerful earthquakes occur”


From Horizon The EU Research and Innovation Magazine

26 April 2021
Caleb Davies

Megathrust earthquakes happen at subduction zones, where one tectonic plate is forced under another. Credit: Marco Reyes / Unsplash.

At 03:34 local time on 27 February 2010, Chile was struck by one of the most powerful earthquakes in a century. The shock triggered a tsunami, which devastated coastal communities. The combined events killed more than 500 people. So powerful was the shaking that, by one NASA estimate, it shifted Earth’s axis of spin by a full 8 cm.

Like nearly all the of the most powerful earthquakes, this was a megathrust earthquake. These happen at subduction zones, places where one tectonic plate is forced under another. If the plates suddenly slip – wallop, you get a massive earthquake. The 2010 Chile quake was a magnitude 8.8: strong enough to shift buildings off their foundations.

We understand subduction zones poorly, which is why geophysicist Professor Anne Socquet, based at Grenoble Alps University [Université Grenoble Alpes] (FR), had planned to visit Chile. She wanted to install seismic monitoring instruments to collect data. By coincidence, she arrived just a week after the quake. ‘It was terrifying,’ she said. ‘The apartment we had rented had fissures in the walls that you could put your fist inside.’

Most people who study megathrust quakes focus on the foreshocks that immediately precede the main quake, Prof. Socquet says. But an unusual feature of megathrust quakes is that they are often followed by a series of other very powerful megathrust quakes several years later and with epicentres hundreds of kilometres away. The 2010 Chile quake, for instance, was followed by other events in 2014, 2015 and 2016 centred on areas up and down the Chile coast. Prof. Socquet wanted to look at these sequences of megathrust earthquakes and investigate the potential links between those great quakes. This requires a careful examination of seismological and geodetic data at a greater scale than has previously been done.


We know that megathrust quakes are the result of the subduction of one tectonic plate below another. But beyond that, we have very little understanding of the dynamics of the subduction and how it might trigger an instability that leads to another megathrust event a few years later. There is some evidence that it could be to do with the release and migration of fluids at great depth. Prof. Socquet’s DEEP-trigger project is about filling that gap. ‘This is kind of virgin territory in terms of observations,’ she said.

The first step of the six-month-old project was supposed to be adding to the network of about 250 GPS instruments that she has contributed to in Chile since 2007 and building a new instrument network in Peru. Currently unable to travel to South America due to the Covid-19 pandemic, she’s been working with local contacts to begin the installation. She’s also working on computational tools to begin analysing legacy data from the region.

‘The critical thing will be to have systematic observations of the link between the slow slip and the seismic fractures at large time and space scales. This will be a very big input to science.’

At the University of Pavia in Italy, mineralogist Professor Matteo Alvaro is also interested in megaquakes – albeit much, much older ones.

It turns out that we can get a unique window on subduction zones as they were millions of years ago. There are certain places, few and far between, where rocks that have been through subduction zones are forced up to the surface. By analysing these rocks we can deduce the depths and pressures at which the subduction happened and build up a picture of how subduction works – and maybe how megathrust earthquakes are triggered.

Prof. Alvaro has just demonstrated the first successful application of a combination of x-ray crystallography and a technique called Raman spectroscopy with a sample of a rock from a location known as the Mir pipe in Siberia. Image credit – Vladimir, licensed under CC BY 3.0.


It usually works like this. Geologists find a rock made of a mineral with what’s called an inclusion crystal inside it. This inclusion was trapped inside the mineral as two subducting plates squeezed each other at great depth, perhaps 100 km or more below the surface. It will have a particular crystal structure – a specific, repeating spatial arrangement of atoms – which depends on the pressure it experienced as it formed. The crystal can reveal the pressure the inclusion was exposed to and hence depth it was formed at.

The trouble is, this is an over simplification. It only holds if the inclusion is cube-shaped – and it almost never is. This whole idea of pressure equals depth – we all know this might be incorrect, says Prof. Alvaro. ‘The natural questions is, okay, but by how much are we wrong?’ That’s what he decided to find out in his project TRUE DEPTHS.

The plan was simple in principle. Prof Alvaro wanted to measure the strain experienced by the crystal while still trapped inside the mineral. If he could understand the tiny displacement of the atoms from their usual positions in a typical, unpressurised crystal structure, that would provide a better measure of the stress applied by the surrounding rock as the crystal was formed and so a more accurate measure of the depth at which it was formed. To study the atomic structure, he uses a combination of x-ray crystallography and a technique called Raman spectroscopy.

Prof. Alvaro has just demonstrated the first successful application of his techniques. He looked at a sample of a rock from a location known as the Mir pipe in Siberia. This is a shaft of molten kimberlite rock that rose very fast from huge depths. (We get most of our diamonds from kimberlite pipes like this, and indeed, Mir has been mined extensively.) Prof. Alvaro looked at rocks of garnet with a tiny quartz inclusions inside that were brought up. ‘The kimberlite is the elevator that brings it to the surface,’ he said.


By measuring the strain on the inclusions, he could confirm it formed at pressure of 1.5 gigaPascals (about 15,000 times that found at Earth’s surface) and a temperature of 850oC. This isn’t entirely surprising, but it is the first proof that Prof. Alvaro’s technique really works. He is now looking to make more measurements and build a library of examples.

He also wonders, more speculatively, if it’s possible that the formation and deformation of the inclusions might act as the very first trigger of megathrust earthquakes. The idea would be that these tiny changes set off cracks in larger rocks that eventually lead a fault to slip out of place. Prof. Alvaro is planning to explore this further.

‘No one knows what the initial trigger is, the thing that triggers the first slip,’ said Prof. Alvaro. ‘We started thinking – and maybe it’s a completely crazy idea – that maybe it’s these inclusions. A cluster of them, maybe subject to an instantaneous phase change and so a change in volume. Maybe that could be the very first trigger.’


Earthquake Alert


Earthquake Alert

Earthquake Network project is a research project which aims at developing and maintaining a crowdsourced smartphone-based earthquake warning system at a global level. Smartphones made available by the population are used to detect the earthquake waves using the on-board accelerometers. When an earthquake is detected, an earthquake warning is issued in order to alert the population not yet reached by the damaging waves of the earthquake.

The project started on January 1, 2013 with the release of the homonymous Android application Earthquake Network. The author of the research project and developer of the smartphone application is Francesco Finazzi of the University of Bergamo, Italy.

Get the app in the Google Play store.

Smartphone network spatial distribution (green and red dots) on December 4, 2015

Meet The Quake-Catcher Network

QCN bloc

Quake-Catcher Network

The Quake-Catcher Network is a collaborative initiative for developing the world’s largest, low-cost strong-motion seismic network by utilizing sensors in and attached to internet-connected computers. With your help, the Quake-Catcher Network can provide better understanding of earthquakes, give early warning to schools, emergency response systems, and others. The Quake-Catcher Network also provides educational software designed to help teach about earthquakes and earthquake hazards.

After almost eight years at Stanford, and a year at CalTech, the QCN project is moving to the University of Southern California Dept. of Earth Sciences. QCN will be sponsored by the Incorporated Research Institutions for Seismology (IRIS) and the Southern California Earthquake Center (SCEC).

The Quake-Catcher Network is a distributed computing network that links volunteer hosted computers into a real-time motion sensing network. QCN is one of many scientific computing projects that runs on the world-renowned distributed computing platform Berkeley Open Infrastructure for Network Computing (BOINC).

The volunteer computers monitor vibrational sensors called MEMS accelerometers, and digitally transmit “triggers” to QCN’s servers whenever strong new motions are observed. QCN’s servers sift through these signals, and determine which ones represent earthquakes, and which ones represent cultural noise (like doors slamming, or trucks driving by).

There are two categories of sensors used by QCN: 1) internal mobile device sensors, and 2) external USB sensors.

Mobile Devices: MEMS sensors are often included in laptops, games, cell phones, and other electronic devices for hardware protection, navigation, and game control. When these devices are still and connected to QCN, QCN software monitors the internal accelerometer for strong new shaking. Unfortunately, these devices are rarely secured to the floor, so they may bounce around when a large earthquake occurs. While this is less than ideal for characterizing the regional ground shaking, many such sensors can still provide useful information about earthquake locations and magnitudes.

USB Sensors: MEMS sensors can be mounted to the floor and connected to a desktop computer via a USB cable. These sensors have several advantages over mobile device sensors. 1) By mounting them to the floor, they measure more reliable shaking than mobile devices. 2) These sensors typically have lower noise and better resolution of 3D motion. 3) Desktops are often left on and do not move. 4) The USB sensor is physically removed from the game, phone, or laptop, so human interaction with the device doesn’t reduce the sensors’ performance. 5) USB sensors can be aligned to North, so we know what direction the horizontal “X” and “Y” axes correspond to.

If you are a science teacher at a K-12 school, please apply for a free USB sensor and accompanying QCN software. QCN has been able to purchase sensors to donate to schools in need. If you are interested in donating to the program or requesting a sensor, click here.

BOINC is a leader in the field(s) of Distributed Computing, Grid Computing and Citizen Cyberscience.BOINC is more properly the Berkeley Open Infrastructure for Network Computing, developed at UC Berkeley.

Earthquake safety is a responsibility shared by billions worldwide. The Quake-Catcher Network (QCN) provides software so that individuals can join together to improve earthquake monitoring, earthquake awareness, and the science of earthquakes. The Quake-Catcher Network (QCN) links existing networked laptops and desktops in hopes to form the worlds largest strong-motion seismic network.

Below, the QCN Quake Catcher Network map
QCN Quake Catcher Network map

ShakeAlert: An Earthquake Early Warning System for the West Coast of the United States

The U. S. Geological Survey (USGS) along with a coalition of State and university partners is developing and testing an earthquake early warning (EEW) system called ShakeAlert for the west coast of the United States. Long term funding must be secured before the system can begin sending general public notifications, however, some limited pilot projects are active and more are being developed. The USGS has set the goal of beginning limited public notifications in 2018.

Watch a video describing how ShakeAlert works in English or Spanish.

The primary project partners include:

United States Geological Survey
California Governor’s Office of Emergency Services (CalOES)
California Geological Survey
California Institute of Technology
University of California Berkeley
University of Washington
University of Oregon
Gordon and Betty Moore Foundation

The Earthquake Threat

Earthquakes pose a national challenge because more than 143 million Americans live in areas of significant seismic risk across 39 states. Most of our Nation’s earthquake risk is concentrated on the West Coast of the United States. The Federal Emergency Management Agency (FEMA) has estimated the average annualized loss from earthquakes, nationwide, to be $5.3 billion, with 77 percent of that figure ($4.1 billion) coming from California, Washington, and Oregon, and 66 percent ($3.5 billion) from California alone. In the next 30 years, California has a 99.7 percent chance of a magnitude 6.7 or larger earthquake and the Pacific Northwest has a 10 percent chance of a magnitude 8 to 9 megathrust earthquake on the Cascadia subduction zone.

Part of the Solution

Today, the technology exists to detect earthquakes, so quickly, that an alert can reach some areas before strong shaking arrives. The purpose of the ShakeAlert system is to identify and characterize an earthquake a few seconds after it begins, calculate the likely intensity of ground shaking that will result, and deliver warnings to people and infrastructure in harm’s way. This can be done by detecting the first energy to radiate from an earthquake, the P-wave energy, which rarely causes damage. Using P-wave information, we first estimate the location and the magnitude of the earthquake. Then, the anticipated ground shaking across the region to be affected is estimated and a warning is provided to local populations. The method can provide warning before the S-wave arrives, bringing the strong shaking that usually causes most of the damage.

Studies of earthquake early warning methods in California have shown that the warning time would range from a few seconds to a few tens of seconds. ShakeAlert can give enough time to slow trains and taxiing planes, to prevent cars from entering bridges and tunnels, to move away from dangerous machines or chemicals in work environments and to take cover under a desk, or to automatically shut down and isolate industrial systems. Taking such actions before shaking starts can reduce damage and casualties during an earthquake. It can also prevent cascading failures in the aftermath of an event. For example, isolating utilities before shaking starts can reduce the number of fire initiations.

System Goal

The USGS will issue public warnings of potentially damaging earthquakes and provide warning parameter data to government agencies and private users on a region-by-region basis, as soon as the ShakeAlert system, its products, and its parametric data meet minimum quality and reliability standards in those geographic regions. The USGS has set the goal of beginning limited public notifications in 2018. Product availability will expand geographically via ANSS regional seismic networks, such that ShakeAlert products and warnings become available for all regions with dense seismic instrumentation.

Current Status

The West Coast ShakeAlert system is being developed by expanding and upgrading the infrastructure of regional seismic networks that are part of the Advanced National Seismic System (ANSS); the California Integrated Seismic Network (CISN) is made up of the Southern California Seismic Network, SCSN) and the Northern California Seismic System, NCSS and the Pacific Northwest Seismic Network (PNSN). This enables the USGS and ANSS to leverage their substantial investment in sensor networks, data telemetry systems, data processing centers, and software for earthquake monitoring activities residing in these network centers. The ShakeAlert system has been sending live alerts to “beta” users in California since January of 2012 and in the Pacific Northwest since February of 2015.

In February of 2016 the USGS, along with its partners, rolled-out the next-generation ShakeAlert early warning test system in California joined by Oregon and Washington in April 2017. This West Coast-wide “production prototype” has been designed for redundant, reliable operations. The system includes geographically distributed servers, and allows for automatic fail-over if connection is lost.

This next-generation system will not yet support public warnings but does allow selected early adopters to develop and deploy pilot implementations that take protective actions triggered by the ShakeAlert notifications in areas with sufficient sensor coverage.


The USGS will develop and operate the ShakeAlert system, and issue public notifications under collaborative authorities with FEMA, as part of the National Earthquake Hazard Reduction Program, as enacted by the Earthquake Hazards Reduction Act of 1977, 42 U.S.C. §§ 7704 SEC. 2.

For More Information

Robert de Groot, ShakeAlert National Coordinator for Communication, Education, and Outreach

Learn more about EEW Research

ShakeAlert Fact Sheet

ShakeAlert Implementation Plan



About Early Warning Labs, LLC

Early Warning Labs, LLC (EWL) is an Earthquake Early Warning technology developer and integrator located in Santa Monica, CA. EWL is partnered with industry leading GIS provider ESRI, Inc. and is collaborating with the US Government and university partners.

EWL is investing millions of dollars over the next 36 months to complete the final integration and delivery of Earthquake Early Warning to individual consumers, government entities, and commercial users.

EWL’s mission is to improve, expand, and lower the costs of the existing earthquake early warning systems.

EWL is developing a robust cloud server environment to handle low-cost mass distribution of these warnings. In addition, Early Warning Labs is researching and developing automated response standards and systems that allow public and private users to take pre-defined automated actions to protect lives and assets.

EWL has an existing beta R&D test system installed at one of the largest studios in Southern California. The goal of this system is to stress test EWL’s hardware, software, and alert signals while improving latency and reliability.

Earthquake Early Warning Introduction

The United States Geological Survey (USGS), in collaboration with state agencies, university partners, and private industry, is developing an earthquake early warning system (EEW) for the West Coast of the United States called ShakeAlert. The USGS Earthquake Hazards Program aims to mitigate earthquake losses in the United States. Citizens, first responders, and engineers rely on the USGS for accurate and timely information about where earthquakes occur, the ground shaking intensity in different locations, and the likelihood is of future significant ground shaking.

The ShakeAlert Earthquake Early Warning System recently entered its first phase of operations. The USGS working in partnership with the California Governor’s Office of Emergency Services (Cal OES) is now allowing for the testing of public alerting via apps, Wireless Emergency Alerts, and by other means throughout California.

ShakeAlert partners in Oregon and Washington are working with the USGS to test public alerting in those states sometime in 2020.

ShakeAlert has demonstrated the feasibility of earthquake early warning, from event detection to producing USGS issued ShakeAlerts ® and will continue to undergo testing and will improve over time. In particular, robust and reliable alert delivery pathways for automated actions are currently being developed and implemented by private industry partners for use in California, Oregon, and Washington.

Earthquake Early Warning Background

The objective of an earthquake early warning system is to rapidly detect the initiation of an earthquake, estimate the level of ground shaking intensity to be expected, and issue a warning before significant ground shaking starts. A network of seismic sensors detects the first energy to radiate from an earthquake, the P-wave energy, and the location and the magnitude of the earthquake is rapidly determined. Then, the anticipated ground shaking across the region to be affected is estimated. The system can provide warning before the S-wave arrives, which brings the strong shaking that usually causes most of the damage. Warnings will be distributed to local and state public emergency response officials, critical infrastructure, private businesses, and the public. EEW systems have been successfully implemented in Japan, Taiwan, Mexico, and other nations with varying degrees of sophistication and coverage.

Earthquake early warning can provide enough time to:

Instruct students and employees to take a protective action such as Drop, Cover, and Hold On
Initiate mass notification procedures
Open fire-house doors and notify local first responders
Slow and stop trains and taxiing planes
Install measures to prevent/limit additional cars from going on bridges, entering tunnels, and being on freeway overpasses before the shaking starts
Move people away from dangerous machines or chemicals in work environments
Shut down gas lines, water treatment plants, or nuclear reactors
Automatically shut down and isolate industrial systems

However, earthquake warning notifications must be transmitted without requiring human review and response action must be automated, as the total warning times are short depending on geographic distance and varying soil densities from the epicenter.


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