From temblor: “Hunga-Tonga-Hunga-Ha’apai in the south Pacific erupts violently”


From temblor

January 18, 2022
Marie Edmonds, Ph.D., The University of Cambridge (UK)

The Hunga-Tonga-Hunga-Ha’apai volcano, 40 miles (65 kilometers) north of Tongatapu, Tonga, erupted on January 15 at 5:14 p.m. local time, triggering tsunami waves that swept across the Pacific. The energy released in the eruption was equivalent to a magnitude-5.8 earthquake at the surface, according to the U.S. Geological Survey. The powerful eruption was captured on satellite images, which show a shock wave and a rapidly expanding ash cloud that reached 12 miles (20 kilometers) into the atmosphere.

The expanding ash cloud from the eruption of the Hunga-Tonga-Hunga-Ha’apai volcano on January 15. Credit: The National Oceanic and Atmospheric Administration (US), Public Domain, via Wikimedia Commons.

News of the immediate impact of the eruption on the Tongan islands has been slow to emerge because internet communications have been entirely cut off by the eruption. It is likely, however, that the islands have experienced many inches of ash fall as well as damage from the tsunami, which inundated coastal areas and reached a height of 2.7 feet (83 centimetres) in Nuku’alofa, according to The Pacific Tsunami Warning Center (US).

The island of Tongatapu and the nearby smaller islands – all part of the Kingdom of Tonga archipelago in the southern Pacific Ocean – are pictured in this Sentinel-2A image from May 23, 2016. Contains modified Copernicus Sentinel data (2016), processed by ESA,CC BY-SA 3.0 IGO, via Wikimedia Commons

ESA Copernicus Sentinel-2.

Tsunami waves reached 3.6 feet (1.1 meters) along the northeastern coastline of Japan at a port in Kuji, Iwate (Source: Japan Meteorological Agency) and up to 3.6 feet (1.1 meters) in Port San Luis, California (Source: NOAA). In northern Peru, two people drowned when waves inundated a beach in the Lambayeque region.

Explosion detected on the other side of the world

The eruption was heard in New Zealand. The shock wave was violent enough to shake houses in Fiji, more than 450 miles (720 kilometers) away from Tonga.

Pressure surges from the atmospheric perturbation caused by the eruption were felt right across the world. Atmospheric pressure fluctuations have been reported in New Zealand, the U.S., Brazil, Japan and Europe. More than 14 hours after the eruption, The Meteorological Office (UK) picked up several pressure waves, more than 10,000 miles away from the volcano. The agency described the waves as “like dropping a pebble in a still pond and seeing the ripples.”

The eruption was so powerful it destroyed the subaerial part of the volcano that had been built up in successive eruptions since 2015, according to the Smithsonian’s Global Volcanism Program. Radar images of the island acquired by The European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganisation](EU)’s Sentinel-2 satellite show that the island has largely disappeared following the eruption; only the far southwestern and northeastern tips of the island remain.

Before (left) and after (right) radar images of the Hunga Tonga-Hunga Haapai Volcano, Tonga, January 2 and 17, 2022. Credit: Copernicus/ESA/Sentinal Hub.

Long-term climate impacts unlikely

The ash produced by the eruption has now dispersed from the caldera, but the finest particles are likely still aloft high in the atmosphere and will remain there for months or even years.

The eruption also produced around 0.4 teragrams of sulfur dioxide (SO2), according to spectrometer data from ESA’s Sentinel 5P satellite.

ESA Copernicus Sentinel-5P.

Past large explosive eruptions have typically been associated with global cooling. SO2 injected into the stratosphere — the second layer of the atmosphere — forms sulfate aerosol when it reacts with water, which absorbs and scatters incoming radiation from the sun, thereby cooling the Earth’s surface.

The 1991 eruption of Pinatubo Volcano in the Philippines emitted around 18-19 teragrams of SO2, which caused cooling of a few tenths of a degree for a few years. It is unlikely that the SO2 emitted from the Hunga-Tonga-Hunga-Ha’apai eruption will significantly impact the climate.

One volcano in a chain

The Hunga-Tonga-Hunga-Ha’apai volcano lies along the Tonga-Kermedec Arc, where two tectonic plates in the southwest Pacific converge. This volcano is one of a chain of largely submarine volcanoes that extend all the way from New Zealand in the southwest to Fiji in the north-northeast. Here, the Pacific plate subducts beneath the Indo-Australian plate. As it sinks, the Pacific Plate heats up, releasing fluids into the overlying rocks, which causes them to melt. The magma rises into the overlying crust and some erupts at the surface. Eruptions from subduction zone volcanoes are notoriously explosive because magmas there are sticky and contain large quantities of dissolved water from the mantle, which is the explosion’s “fuel.”

Map of the Kermadec and Tonga subduction trench. Credit: Nwbeeson, CC BY-SA 4.0, via Wikimedia Commons.

For submarine volcanic eruptions however, there is an added ingredient that causes them to be extra-violent. During large volcanic eruptions a caldera, or large depression on the surface, can form due to the void left in the ground by the erupted magma. Calderas that form on the seafloor can cause tsunamis and large earthquakes when large rock masses sink during the eruption.

Seawater can flow into the faults and fractures that form around the edges of the caldera. If water comes into contact with hot magma, it flash boils into steam, which expands rapidly, adding to the explosive power of an eruption. Such eruptions are termed “hydrovolcanic.” They generate powerful base surges — or pyroclastic flows — that expand out from the base of the eruption column, and can travel long distances. A famous example is the 1883 eruption of Krakatoa Volcano in Indonesia. The sound of the explosion was heard 1,800 miles (3,000 kilometers) away. Large tsunami waves and pyroclastic surges that travelled 25 miles (40 kilometers) over the surface of the sea killed more than 36,000 people.

Geologists studying the Hunga-Tonga-Hunga-Ha’apai volcano have uncovered its few-thousand-year-long history of eruptions just like the one that occurred on January 15. The volcano erupted explosively in 2009 and in 2014-2015, producing ‘Surtseyan’ eruptions — a smaller magnitude explosive eruption produced by the interaction of magma and seawater. The precise magnitude of this latest eruption will be known once the height of the eruption column as well as the volume of erupted material is estimated, but it is certainly one of the most significant eruptions of the 21st century thus far.

NASA’s Terra satellite on December 29, 2014, showing a white plume rising over the undersea volcano Hunga Ha’apai, near Hunga Tonga in the South Pacific. Discolored water suggests an underwater release of gases and rock by the eruption. Credit: NASA, CC0, via Wikimedia Commons.

National Aeronautics Space Agency (US)Terra satellite.

Answers still to come

There are many questions to be answered over the coming weeks and months about the mechanisms and impacts of this eruption. Immediate questions concern the fate of the residents of Tonga, who are contending with the enormous challenges of the aftermath of the eruption and tsunami, including missing loved ones, enormous infrastructure damage, thick ash cover, contaminated drinking supplies and a lack of basic medical and communication services.

There will be detailed studies of the geophysical signals accompanying the eruption and the period leading up to it to better understand how the eruption was triggered and its magnitude. Scientists will be particularly interested in infrasound, satellite-based data and eventually will study the volcanic deposits and landforms produced. In particular, scientists will seek to understand the geological sequence of events that led to the simultaneous explosion and tsunami that had such wide-ranging effects across the Pacific Ocean.


Guo, S., Bluth, G. J., Rose, W. I., Watson, I. M., & Prata, A. J. (2004). Re‐evaluation of SO2 release of the 15 June 1991 Pinatubo eruption using ultraviolet and infrared satellite sensors. Geochemistry, Geophysics, Geosystems, 5(4).

See the full article here .


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Stem Education Coalition


Earthquake Alert


Earthquake Alert

Earthquake Network project Earthquake Network 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.