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Abstract Number
T4.1-P18.
Preliminary Study of the CTBTO’s Seismic Station Characteristics
Using Spectral Analysis Method in Indonesia
B. Wibowo, N. Heryandoko, S. Rohadi
Abstract.We analysed recording waveform of six seismographics stations which is part of CTBTO's seismic
network in Indonesia. The analysis using the spectral analysis method conducted to determine the charac-
teristics response of each seismographic station. We analyzed background noise level of sites using Power
Spectral Density (PSD) and Probability of Density Function (PDF). The result of spectral analysis indicate
that PSI station (Parapat, Sumatera) has the lowest background noise level, so its has highest Signal To
Noise Ratio (SNR). This station has best recording of nuclear explosion and earthquake event compare to
recording of other station. This good quality of recording signal because the seismometer located on the
representative bedrock and the site good protected from the ambient or environmental noise. Otherwise,
LEM station (Lembang, Bandung) has the highest background noise level and has lowest SNR. LEM sta-
tion located near the Tangkuban Perahu Mountain that one of active vulcano in Bandung. Activity of the
vulcano may create disturbance noise to the recording signal in Lembang station (LEM). The significance
noise also may because of human activity around this site. We also conduct time frequency analysis by
comparing frequency content between nuclear explosion and the earthquake event. The results indicate
that explosion have more clear and focus of spectogram than that of an earthquake events, this character-
istic can be used to identified nuclear explosion accurately.
SEKOLAH TINGGI METEOROLOGI,
KLIMATOLOGI, DAN GEOFISIKA
S T M K G
Figure 4. Frequency response from different type of
seismometer used by CTBTO’ stations in Indonesia.
Figure 1 & 3. The Location of CTBTO’s Auxiliary Sta-
tions in Indonesia, indicate by red triangle and nuclear
explosion and earthquake (yellow star).
.
Table 1. The name, seismometer type, and geo-
graphical coordinat of CTBTO’s Auxilliary Sta-
tions in Indonesia.
(a) (b)
Figure 2. (a) Parameters from the North Korea’s 2013 Nuclear
Test (http://earthquake.usgs.gov/ earthquakes), and (b) Earth-
quake parameters from the Hokkaido’s Earthquake (geofon).
INTRODUCTION We analyzed background noise level of sites using Power Spec-
tral Density (PSD) and Probability of Density Function
(PDF).
Time Frequency Analysis to describe frequency content of nu-
clear event, as well as earthquake event, recorded by these sta-
tions
Estimating the level of effectiveness the stations regarding de-
tection of nuclear and earthquake events.
Using 2 datasets for this research. Each dataset consisted by 6
vertical component records:
First, we used seismic signal recording from 6 stations with
duration about 7 days from April 1st 2015, 00:00:00 UTC
to April 8th 2015, 00:00:00 UTC
Second, we proccessed nuclear event data recorded by
CTBTO’s stations in Indonesia. The North Korea’s 2013
Nuclear Test was held on February 12th 2013 (Figure 2.a).
We also proccessed an earthquake event that occur within
similar distance and magnitude, comparing to nuclear event.
The Earthquake was occured in Hokkaido, March 25, 2015
(Figure 2.b and Figure 3).
All of the data processing on both dataset used Obspy, a seismic
waveform analysis software that based on Python Program.
The Power Spectral Density, Probability of Density Function, Day vs Night Amplitudo Ratio
(i)
(ii) (iii)
(iv)
(v) (vi)
Figure 5. The Result of Power Spectral Density and Probability of Density Function of (i) SIJI, (ii) PSI, (iii) LEM, (iv) KAPI, (v) JAY, (vi) BATI Station.
Figure 6. The Mean Value of PSD from from 6 Stations Figure 7. The ratio between day and night data from all stations
are plotted in a graph.
Figure 9. The graph be-
tween distance from 6 sta-
tions and its time duration
from the North Korea’s
2013 Nuclear Event.
Time Frequency Analysis (Spectrograms) of The North Korea’s 2013 Nuclear Event
(i) (ii)
(iii) (iv)
(v) (vi)
Figure 8. The Time Frequency Spectrogram and Waveform of The
North Korea’s 2013 Nuclear Event of (i) SIJI, (ii) JAY, (iii) KAPI,
(iv) BATI, (v) PSI and (vi) LEM station, respectively.
Time Frequency Analysis’s (Spectrograms) of The Hokkaido Earthquake
(i) (ii)
(iii)
(iv)
(v) (vi)
Figure 10. The Time Frequency Spectrogram and Waveform of
Hokkaido Eartquake of (i) SIJI, (ii) BATI, (iii) JAY, (iv) PSI, (V)
KAPI, and (vi) LEM Station, respectively.
Figure 11. The graph between
distance from 6 stations and its
time duration from the Hokkai-
do Earthquake.
RESULT AND DISCUSSION
LEM Station has the highest background noise level comparing to other stations, otherwise PSI Station has the
lowest one
The signal from nucle-
ar event clearly ap-
peared at KAPI, BATI,
and PSI stations
KAPI and PSI have
same distance (about
47°) to the epicenter
and BATI Station have
same distance to epi-
center (about 52°) with
LEM station, but
BATI station has high-
er SNR rather than
LEM Station.
2 stations has high SNR re-
garding this event, PSI Sta-
tion (10.IV)) and LEM sta-
tion (10.VI)
all station we can still rec-
ognize the signal from this
event better than nuclear
event as shown before,
caused by situation that at
early in the morning, noise
level caused by human ac-
tivity had not increase yet.
LEM station, which has
higher noise level, we can
still see the signal clearly,
but it rather has shorter fre-
quency range compared
with PSI Station.
The writers thank The State College of
Meteorology, Climatology and Geophysics
(STMKG), The Indonesian Meteorology,
Climatology, and Geophysics Agency
(BMKG), for the chances and support dur-
ing the research and The CTBTO’s Sci-
ence and Technology Conference 2015’s
Commitees for the opportunities to present
our research result in their event.
ACKNOWLEDGEMENT
REFERENCES
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(Open-File Report 2005-1438, USGS,
2005)
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