il-young che, hee-il lee* earthquake research center
DESCRIPTION
A Study on Characteristics of Seasonally Dependent Infrasound Propagation Based on the Ground-Truth Events from a Long-Term Experiment at a Quarry mine. Il-young CHE, Hee-il LEE* Earthquake Research Center Korea Institute of Geoscience & Mineral Resources(KIGAM), Daejeon, Korea. - PowerPoint PPT PresentationTRANSCRIPT
A Study on Characteristics of A Study on Characteristics of Seasonally Dependent Seasonally Dependent
Infrasound Propagation Based Infrasound Propagation Based on the Ground-Truth Events on the Ground-Truth Events
from a Long-Term Experiment from a Long-Term Experiment at a Quarry mineat a Quarry mine
A Study on Characteristics of A Study on Characteristics of Seasonally Dependent Seasonally Dependent
Infrasound Propagation Based Infrasound Propagation Based on the Ground-Truth Events on the Ground-Truth Events
from a Long-Term Experiment from a Long-Term Experiment at a Quarry mineat a Quarry mine
Il-young CHE, Il-young CHE, Hee-il LEE*Hee-il LEE*
Earthquake Research CenterEarthquake Research Center Korea Institute of Geoscience & Mineral Resources(KIGAM), Daejeon, KoreaKorea Institute of Geoscience & Mineral Resources(KIGAM), Daejeon, Korea
Presented at 2008 Infrasound Technology WorkshopPresented at 2008 Infrasound Technology WorkshopBermuda, November 3 – November 7, 2008Bermuda, November 3 – November 7, 2008
With the contribution of Dr. Alexis Le PichonWith the contribution of Dr. Alexis Le Pichon
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
516 SA events in 2006 649 SA events in 2007
Increase accuracy of localization of the seismo-acoustic events
Motivation
• Total number of 649 seismic events, i.e., 10% of total seismic events, were discriminated as surface explosion by the seismo-acoustic analysis in 2007
• Most seismo-acoustic events are closely gathered in several regions and show similar distribution pattern to previous years
169 Events
Seismic DataSeismic Data
Infrasound
25
194
341
79 10•0
•50
•100
•150
•200
•250
•300
•350
•N
um
bers
~< 0.5 ~<1.0 ~<1.5 ~<2.0 ~<2.5
•Local magnitude (M•L•)
•Seismic magnitude (M•L•) of SA in 2007
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Developing accurate locator for small seismo-acoustic events
Assessing detectability of the stations
Characterizing infrasound propagation according to season – arrival time, back-azimuth, attenuation, etc
Deriving experimental relationship between charge size and amplitude from source time function
Objectives
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
(37.5478N, 128.9614E)
Experiment at a Quarry Mine (2007-2008)
Deployment of 2 Stations - CMT40T-1, Chaparral M2, Q330 Deployment of 2 Stations - CMT40T-1, Chaparral M2, Q330 Operation :Operation : - 1.5 Month Test in 2006 - from Apr. 2007 -
Blasting Information Blasting Information - Everyday at 3h (UTC) - 0.1~10 tons ANFO
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Experiment at a Quarry Mine (2007-2008)
Station informationStation information
KSGAR (2003) - 11 elements (4)- Distance : 126.9km- Back-azimuth : 155.2°
CHNAR (1999) - 11 elements (4)- Distance : 180.4km- Back-azimuth : 115.8°
BRDAR (2004) - 13 elements (5)- Distance : 383.0km- Back-azimuth : 95.6°
TJIAR (2002) - 4 elements (1)- Distance : 192.7km- Back-azimuth : 47.2°
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Source Time Function (1)
Source signals measured near the blasting point (2007/06/01)Source signals measured near the blasting point (2007/06/01)
- Charge Size : 0.1 t
- Dominant Frequency ~ 2Hz
- P-to-P Amplitude : 39 μbar
- Empirical expression relating acoustic pressure to yield- Calculate source energy- Amplitude attenuation- etc.
Origin Time : 02:55:45.4
Seismic
Infrasound
Air wave
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Source Time Function (2)
Source signals measured near the blasting point (2007/06/15)Source signals measured near the blasting point (2007/06/15)
- Charge Size : 8.0 t
- Dominant Frequency ~ 1.8Hz
- P-to-P Amplitude : Clipped
Aseismic ↔ AinfrasoundSeismic
Infrasound
Air wave
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Data Analysis
Detection & Parameter EstimationDetection & Parameter Estimation
Phase IdentificationPhase Identification
- KSGAR: mainly - KSGAR: mainly Iw, (Is)Iw, (Is)- CHNAR:- CHNAR: Is Is- BRDAR: - BRDAR: Is, IsIs, ItIs, IsIs, It- TJIAR: - TJIAR: IsIs
Based on our previous experience gained in 2006 – expected time Based on our previous experience gained in 2006 – expected time of arrival to the stations and phases, data was analyzed semi-of arrival to the stations and phases, data was analyzed semi-automaticallyautomatically
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Data Analysis by PMCC
Data recorded at CHNAR on 01 June 2007Data recorded at CHNAR on 01 June 2007
Expected arrival time of Is
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Speed: 358 m/sAzimuth: 116.8±0.2°
Speed: 352 m/sAzimuth: 118.6±0.1°
Speed: 352 m/sAzimuth: 116.5±013°
Speed: 358 m/sAzimuth: 116.6±0.2°
Speed: 363 m/sAzimuth: 115.3±0.2°
Speed: 358 m/sAzimuth: 119.2±0.4°
Speed: 355 m/sAzimuth: 118.4±0.3°
Data Analysis by PMCC (01 June 2007)
Unexpected Problem : many signals coming from the same direction in a limited time window
Back-Azimuth : 115.8 °Back-Azimuth : 115.8 °
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Blastings at the nearby mines
Distances in KmDistances in Km(Back Azimuth in Degree(Back Azimuth in Degree))
Study MineStudy Mine Mine AMine A Mine BMine B RemarksRemarks
BRDARBRDAR383.0 95.6
391.5 97.0
404.3 97.4
< 2.o°
CHNARCHNAR180.4 115.8
191.4117.6
204.5 117.2
< 2.o°
KSGARKSGAR126.9155.2
139.4154.4
149.4 151.0
< 5.o°
TJIARTJIAR192.7 47.2
191.350.9
198.0 54.2
<7.2°
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Seasonal Variation of CelerityExactly measured celerity(Is) from mine to CHNAR
: 0.27 km/s (Apr.) 0.29 km/s (Aug.) 0.27 km/s (Oct.) 0.26 km/s (Jan.) 0.27 km/s (Apr. 2008)
The experiment shows first arrival is close to Is phase, guided wave propagating between the stratopause and the ground.
Celerity is strongly depending on seasonal velocity structure in atmosphere. Seasonal dependency of celerity should be considered in the infrasonic location method
600
620
640
660
680
700
2007
-04-
23
2007
-05-
07
2007
-05-
21
2007
-06-
04
2007
-06-
18
2007
-07-
02
2007
-07-
16
2007
-07-
30
2007
-08-
13
2007
-08-
27
2007
-09-
10
2007
-09-
24
2007
-10-
08
2007
-10-
22
2007
-11-
05
2007
-11-
19
2007
-12-
03
2007
-12-
17
2007
-12-
31
2008
-01-
14
2008
-01-
28
2008
-02-
11
2008
-02-
25
2008
-03-
10
2008
-03-
24
Day
Infr
aso
un
d t
rave
l ti
me
s (
s)
Spring timeSpring time
Summer timeSummer time
Autumn timeAutumn time
Winter timeWinter time
November
Spring timeSpring time
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Modelling with ECMWF (in Summer)
2007/06/01_ECMWF91_UVTSPQZ (From mine to CHNAR)TauP & WASP 3D
Z=44.1km, X=192.1/180.4, T=682.04s, Vt=354.55m/s, Vapp=281.65m/s, Daz=0.31°Z=43.5km, X=199.5/180.4, T=702.95s, Vt=351.55m/s, Vapp=283.80m/s, Daz=0.35°
We thank IDC for providing the ECMWF91 data and Dr. Alexis for doing ray-tracing with them.
Slowness
Wind correctedSlowness
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Modelling with ECMWF (in Winter)
2007/12/22_ECMWF91_UVTSPQZ (From mine to CHNAR)TauP & WASP 3D
Z=0.2km, No=36, X=182.1/180.4, T=540.68s, Vt=339.13m/s, Vapp=336.77m/s, Daz=-0.53°Z=0.2km, No=35, X=177.0/180.4, T=525.66s, Vt=339.13m/s, Vapp=336.77m/s, Daz=-0.53°Z=0.2km, No=37, X=187.1/180.4, T=555.70s, Vt=339.13m/s, Vapp=336.77m/s, Daz=-0.53°
Slowness
Wind correctedSlowness
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Why detectability is increasing in Summer?
The experiment also shows detectability in summertime is higher than autumn-winter-spring seasons.It implies that infrasound propagation and detection are related with seasonal wind in and around the Korean Peninsula. We interpret that lower detectability in autumn-winter-spring is due to prevailing NW wind, its direction is opposite to infrasound propagation from the mine to CHNAR.
Detected
Not detected
Observed up to 30km at SokchoObservatory (47090)
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Surface Winds Affects the Detectability?
The wind speed and direction are value averaged over 1 minute window at the time of blasting
Detectability
CHNAR : ~55% (in Summer) ~40% (all over the season)
KSGAR : less than 5%
At least one station : ~ 40%Two stations : ~16%Three stations : ~10%Four stations : < 5%
Do surface wind fields near the source affect the detectability? No!Do surface wind fields near the source affect the detectability? No!
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Localization by SALoc
Seismo-acoustic location method
Location method for small-magnitude surface explosions - generating both seismic and infrasonic signals
Grid search method - finding a location where the time residual between observed and model predicted is minimum at the grid points with initial conditions : origin time, celerity, wind-corrected back-azimuth
An example : location results for 6 tons of ripple-firing shot
,
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Comparison of localization results
Comparison of localization results for 21 ground-truth events
The seismo-acoustic location shows a mean location error of 5.7 km, which represents a substantial improvement in location accuracy of 58.7% and 46.7% compared to the seismic location and infrasonic-azimuth intersection methods, respectively.
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Summary & General Remarks
Detectabilty is increasing in Summer
Long-term measurement over the years will be helpful to clarify seasonal variation of celerity and to study atmospheric effects on infrasound propagation in mid-latitude Northern Hemisphere around the Korean Peninula
Celerity (Is) between CHNAR and mine changes as follows;- 0.27 km/s in April 2007
- 0.29 km/s in August 2007- 0.27 km/s in October 2007- 0.26 km/s in January 2008- 0.27 km/s in April 2008
Most frequently detected phase is Is at the stations of interest
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Summary & General Remarks
SALoc significantly reduces location error for small magnitude explosion, M < 2.0
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
Korea Institute of Geoscience and Korea Institute of Geoscience and Mineral ResourcesMineral Resources
In the Future
Recovering source waveform saturated
Empirical relationship between the amplitude of the source wavelet/energy/measured amplitude
Continue this experiment to the next April to see seasonal change is consistent from year to year