A new way to sense earthquakes could help improve early warning systems
Every year earthquakes worldwide claim hundreds or even thousands of lives. Forewarning allows people to head for safety and a matter of seconds could spell the difference between life and death. UTokyo researchers demonstrate a new earthquake detection method -- their technique exploits subtle telltale gravitational signals traveling ahead of the tremors. Future research could boost early warning systems.
A map of Japan showing locations for the epicenter of the 2011 Tohoku earthquake (✩),Kamioka (K), Matsushiro (M) and seismic survey instruments used (△ and ●).
Credit: ©2019 Kimura Masaya
The shock of the 2011 Tohoku earthquake in eastern Japan still resonates for many. It caused unimaginable devastation, but also generated vast amounts of seismic and other kinds of data. Years later researchers still mine this data to improve models and find novel ways to use it, which could help people in the future. A team of researchers from the University of Tokyo's Earthquake Research Institute (ERI) found something in this data which could help the field of research and might someday even save lives.
It all started when ERI Associate Professor Shingo Watada read an interesting physics paper on an unrelated topic by J. Harms from Istituto Nazionale di Fisica Nucleare in Italy. The paper suggests gravimeters -- sensors which measure the strength of local gravity -- could theoretically detect earthquakes.
"This got me thinking," said Watada. "If we have enough seismic and gravitational data from the time and place a big earthquake hit, we could learn to detect earthquakes with gravimeters as well as seismometers. This could be an important tool for future research of seismic phenomena."
The idea works like this. Earthquakes occur when a point along the edge of a tectonic plate comprising the earth's surface makes a sudden movement. This generates seismic waves which radiate from that point at 6-8 kilometers per second. These waves transmit energy through the earth and rapidly alter the density of the subsurface material they pass through. Dense material imparts a slightly greater gravitational attraction than less dense material. As gravity propagates at light speed, sensitive gravimeters can pick up these changes in density ahead of the seismic waves' arrival.
"This is the first time anyone has shown definitive earthquake signals with such a method. Others have investigated the idea, yet not found reliable signals," elaborated ERI postgraduate Masaya Kimura. "Our approach is unique as we examined a broader range of sensors active during the 2011 earthquake. And we used special processing methods to isolate quiet gravitational signals from the noisy data."
Japan is famously very seismically active so it's no surprise there are extensive networks of seismic instruments on land and at sea in the region. The researchers used a range of seismic data from these and also superconducting gravimeters (SGs) in Kamioka, Gifu Prefecture, and Matsushiro, Nagano Prefecture, in central Japan.
The signal analysis they performed was extremely reliable scoring what scientists term a 7-sigma accuracy, meaning there is only a one-in-a-trillion chance a result is incorrect. This fact greatly helps to prove the concept and will be useful in calibration of future instruments built specifically to help detect earthquakes. Associate Professor Masaki Ando from the Department of Physics invented a novel kind of gravimeter -- the torsion bar antenna (TOBA) -- which aims to be the first of such instruments.
"SGs and seismometers are not ideal as the sensors within them move together with the instrument, which almost cancels subtle signals from earthquakes," explained ERI Associate Professor Nobuki Kame. "This is known as an Einstein's elevator, or the equivalence principle. However, the TOBA will overcome this problem. It senses changes in gravity gradient despite motion. It was originally designed to detect gravitational waves from the big bang, like earthquakes in space, but our purpose is more down-to-earth."
The team dreams of a network of TOBA distributed around seismically active regions, an early warning system that could alert people 10 seconds before the first ground shaking waves arrive from an epicenter 100 km away. Many earthquake deaths occur as people are caught off-guard inside buildings that collapse on them. Imagine the difference 10 seconds could make. This will take time but the researchers continually refine models to improve accuracy of the method for eventual use in the field.
Masaya Kimura; Nobuki Kame; Shingo Watada; Makiko Ohtani; Akito Araya; Yuichi Imanishi; Masaki Ando; Takashi Kugi. Earthquake-induced prompt gravity signals identified in dense array data in Japan. Earth, Planets and Space. DOI: 10.1186/s40623-019-1006-x
This research was supported by JSPS (KAKENHI JP15K13559, JP16K05532, JP18J21734), and MEXT via the Program for Leading Graduate Schools and the Earthquake and Volcano Hazards Observation and Research Program.
Mr. Masaya Kimura
Earthquake Research Institute, The University of Tokyo,
1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032 JAPAN
Ms. Moe Fukui
Outreach and Public Relations Office, Earthquake Research Institute,
The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032 JAPAN
Mr. Rohan Mehra
Division for Strategic Public Relations, The University of Tokyo,
7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, JAPAN
About the University of Tokyo
The University of Tokyo is Japan's leading university and one of the world's top research universities. The vast research output of some 6,000 researchers is published in the world's top journals across the arts and sciences. Our vibrant student body of around 15,000 undergraduate and 15,000 graduate students includes over 2,000 international students. Find out more at https:/
Rohan Mehra | EurekAlert!
USF geoscientists discover mechanisms controlling Greenland ice sheet collapse
22.07.2019 | University of South Florida (USF Innovation)
Welcome Committee for Comets
19.07.2019 | Technische Universität Braunschweig
Augsburg chemists and physicists report how they have succeeded in the extremely difficult separation of hydrogen and deuterium in a gas mixture.
Thanks to the Surface Acoustic Wave (SAW) technology developed here and already widely used, the University of Augsburg is internationally recognized as the...
Adjusting the thermal conductivity of materials is one of the challenges nanoscience is currently facing. Together with colleagues from the Netherlands and Spain, researchers from the University of Basel have shown that the atomic vibrations that determine heat generation in nanowires can be controlled through the arrangement of atoms alone. The scientists will publish the results shortly in the journal Nano Letters.
In the electronics and computer industry, components are becoming ever smaller and more powerful. However, there are problems with the heat generation. It is...
Scientists have visualised the electronic structure in a microelectronic device for the first time, opening up opportunities for finely-tuned high performance electronic devices.
Physicists from the University of Warwick and the University of Washington have developed a technique to measure the energy and momentum of electrons in...
Scientists at the University Würzburg and University Hospital of Würzburg found that megakaryocytes act as “bouncers” and thus modulate bone marrow niche properties and cell migration dynamics. The study was published in July in the Journal “Haematologica”.
Hematopoiesis is the process of forming blood cells, which occurs predominantly in the bone marrow. The bone marrow produces all types of blood cells: red...
For some phenomena in quantum many-body physics several competing theories exist. But which of them describes a quantum phenomenon best? A team of researchers from the Technical University of Munich (TUM) and Harvard University in the United States has now successfully deployed artificial neural networks for image analysis of quantum systems.
Is that a dog or a cat? Such a classification is a prime example of machine learning: artificial neural networks can be trained to analyze images by looking...
24.06.2019 | Event News
29.04.2019 | Event News
17.04.2019 | Event News
22.07.2019 | Power and Electrical Engineering
22.07.2019 | Life Sciences
22.07.2019 | Life Sciences