World Bosai Forum 2019, Sendai
Nov. 10, 2019
MP1-02

Proposition of a New Ground-based
Observation Network of Infrasoundfor Tsunami Disaster Mitigation
Masa-yuki YAMAMOTO
Kochi University of Technology, JAPANInfrasound: long-distant propagating waves
AGW | Sound• frequency
1. Thunderstorms
2. TLEs (sprites, elves,..)3. Meteorite falls, artificial reentries
4. Volcanic eruptions
5. Artificial explosions
6. Coupling process fromseismic/oceanic waves
7. Earthquakes, Tsunamis

Lower cutoff：1 gf 2 2cElves
Meteorites
Sprites
cumulonimbus
CloudsVolcaniceruptions

Thunderstorms

γ:1.4
Tsunamisg: gravity
Artificial
c: sound speed
Earthquakes
explosions

Targets of infrasound observation network• 25 km scale sensor array distribution in each prefecture• Obtaining information for Tsunami disaster mitigation• Remote sensing for local geophysical events
•
•
•
•
•
•
•
•
•

Thunderstorm
Heavy rainy band
Typhoon/Front passage
Volcanic eruptions
Tsunami, Earthquake
Meteoroids, Re-entry
Microbaroms (oceanic)
Artificial sourcesWind Turbine Noise-> Weather forecast (Alert)-> Disaster Mitigation (Alert)-> Geophysics, Astrophysics,

Aerospace Engineering,-> Environmental study,
Effect on Human healthGreat East Japan Earthquake and Tsunami on March 11, 2011

CNN (NHK)Arai et al., 2011

Expectation of an alert system for Tsunami disaster
Infrasound waves can reach to the land stations
earlier than the real Tsunami waves.
It can be applied not only for the Tsunami alert
system but also for any other geophysical event
monitor.
Infrasound in middle/upper atmosphereSensors

50 km

Infrasound

200 km音波源

Infrasonic waves vibrate ionosphere
Tsugawa et al., 2011

Frequency

Elves

MeteoritesFireballs< 20 Hz
TLE (Sprites)

Propagates
longdistance

Volcanic
eruptionsThunderstorms~ 1000 km

Microbaroms
Artificial
explosions

Landslides
Earthquakes

Sources of Infrasonic waves

TsunamiFor an application for disaster prevention/mitigation• Infrasound observation is one of the useful remote-sensing methods in theatmosphere.
• In particular, for the Tsunami disaster, it can propagate source region
information by sound speed faster than the real sea waves, thus an advantage
in early warning system can be expected.

Prefecture level dense infrasound observation network in Kochi
15 sites in operation mainly for Tsunami disaster mitigationo since 2016
＊ since 2017

Kochi Univ. of Tech.

Kochi
Solid line: 2 km scale
Dotted: 8 km scale
Broken: 25 km scaleo＊＊＊TosaAki＊＊

Nankoku
Konan

＊

Toyo
＊ Muroto

SukumoKuroshio（5 -> 3sites）
o oooo＊Tsunami simulation
After 30 minutes

Ashizuri＊＊＊ （３ sites）（Kuroshio town）（Kai et al., 2015）

Quick Look
web pageforinfrasonicobservationis on web.

Infrasound coming from Mt. Aso

Overpressure

50Vertical [km]403020100050

100
150
200
Horizontal [km]250TimeInfrasound signal coming from a volcanic eruption of Mt. Aso (Oct. 8, 2016)
Overpressure of 189 Pa was observed at 1:46:41 at 1.2 km from the chamber. (JMA)
Mt. Aso -> Kuroshio town： 180 km, Surface path @340 m/s（ 15℃） 1:55:26
Mt. Aso -> KUT campus： 257 km, Stratospheric path @317 m/s（-24℃） 2:01:23

12300

Volcanic eruption of Mt. Sakurajima

Ash top: 4700 m© Kyodo Press
Infrasound:
24 Pa at JMA Yokoyama site
Distance from Sakurajima
243 km Sukumo
255 km Tosashimizu 3
275 km Kuroshio 3
332 km Tosa
341 km Kochi
372 km Aki

Examples of estimating Sakurajima volcanic eruption sound source
Assuming sound velocity of 336.2 m/s (by using our previous dataset in 2012)• 55 events are found by N-type signal detection software.
• 38 cases are found near the volcanic center within a few km by using theGrid search method.

14

An example of Grid search for volcanic infrasoundCorrelation value

spike

Correlation value

spikeTime difference [second]

Time difference [second]• The method is usually used in seismology.
• Grid search is a method of dividing a region into multiple grids (here,15749×1766 grids) and searching for a grid with the smallest error

Infrasound data before and during
a Typhoon passage in 2016

3 days trend

1 hour wave form

3 days spectrum

Infrasound signal detected when a Typhoon strikes
Kochi prefecture on Sep. 4, 2018
Typhoon passage (No.21)
Over 100 Pa &over 30 min.
at Muroto
capeRain band radar © Yahoo JAPANLocal heavy rain band passage was only/clearly observedat Toyo town on Aug. 17, 2018.

Rain band radar © Yahoo JAPANThunder monitoring via Infrasound Kochi Univ. of Tech.

・5 ch meteor interferometer

・Infrasound sensor
・Video camera
 Geisei observatory

・Meteor radio observation
・Infrasound sensor

・Video camera Otoyo town

・Meteor radio observation

・Infrasound sensor

19

Kochi Univ. of tech.

Geisei observatory

Otoyo town

0KU

-10T-20

Power [dB]

-30
-40
-50

Fig. 4 各地点で観測されたインフラサウンド-60-70-80-90-100
051015202530

Frequency [Hz]35404550

20

Thunder point
Event time

18 h 59 m 31.9 s

Observation point

Observation time

Azimuth141.97°KUT

18 h 59 m 51.6 s

Latitude33.58°

Geisei18 h 59 m 55.2 s

Altitude2104 mOtoyo

19 h 00 m 45.8 s

Distance(KUT)

6351 mDistance(Geisei)

7715 mDistance(Otoyo)

24396 m21

Sweden-Japan collaborative balloon
experiment BEXUS-EXIST (Oct. 2017)

SAYA INF03
Microphone array
for BEXUS/EXIST
Mass: 127 g
Freq.: 0.01 Hz – 20 Hz

MOMO2 sounding rocket
June 30, 2018-> Exploded!!

© インターステラテクノロジズ

花火© インターステラテクノロジズ

音波伝搬

MOMO2 rocket on June 30, 2018

Energy estimation of MOMO2 rocket explosion

170 Pa p-p overpressure detected at a sensor locatedat 50 m from the rocket explosion point on ground.

The energy was about 710 kJ.
(170 g of TNT bomb level)
It seems NO severe explosion.
Only liquid Oxygen tank broken.
Without mixing full of fuel andliquid Oxygen.

We successfully measured energy of the rocket explosion…(-_-)

Momo3: 1st Japanese venture company’s rocket over 100 km in space!
(with our microphones) on May 4, 2019

Test infrasound measurement in Europe(Sep. 8, 2019 at Mechelen, Belgium)

New sensor:
SAYA INF04LE

Summary• We believe infrasound observation is extremely
important for disaster mitigation for many types ofgeophysical events like tsunami or thunderstorm.
• By using prefecture level dense infrasound sensor
network in Kochi, a typhoon strike and its affection
on infrasound measurement was clearly observed.
• We checked overpressure datasets for MOMO2
rocket explosion and estimated explosive energy
by using calibrated infrasound sensors on ground.
• Artificial explosions of fireworks were measured inupper atmosphere by infrasound sensors aboard
MOMO3 sounding rocket.

Acknowledgements• Infrasound research projects shown here
are partly supported with JSPS KAKENHI(Grant-in-Aid for Scientific Research B),
JST Matching Planner scheme, MIC
SCOPE scheme, and research grant bySECOM Foundation for Science &Technology.