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T4.1-P29 UNDERSTANDING THE AMPLITUDES OF SEISMIC SIGNALS AND STATION NOISE Michael E. Pasyanos, William R. Walter, Eric M. MatzelLawrence Livermore National Laboratory
Attenuation Models
LLNL has engaged in a multiyear effort to measure regional phase (Pn, Pg, Sn, Lg) seismic amplitudes in order to accurately map out the attenuation structure of the lithosphere. Each phase has different sensitivity, allowing us to tomographically map out the Qp and Qs structure of the crust and upper mantle. The ultimate goal is the development of a high-resolution global lithospheric attenuation model.
Station Noise
Station noise varies widely and must be accounted for. We estimate station noise by running statistics on pre-event noise measurements in multiple frequency bands. Some stations have sensitivity to time of day or time of year.
Can We Detect It? - one P-wave
A single signal above the noise at any particular frequency is enough to detect an event. Here,we compare SNR for a singlefrequency band (6-8 Hz) anda broad frequency band (0.5-8 Hz)
Can We Locate It? - three or four P-waves
In order to locate an event, one needs three P-wave detections, or four if one is not fixing the depth.These figures show SNR for thethird and fourth largest regionalsignals.
Can We Identify or Screen It? - one S-wave
The ratio of high-frequency regional P/S waves has been found to be an effective way of separating earthquake and explosion populations, but the S-wave (Sn or Lg) needs to be above the noise.
NOTE: SNRs of secondary phases shownhere are calculated relative to pre-event noise rather than pre-phase noise.
Can We Estimate its Size? - one S-wave coda
The coda waves of S-waves have been found to be a stable estimator of earthquake size, but a duration of the signal needs to be above the noise.Here, we estimate the SNR of thedirect phase and the signal 50 s intothe coda.
Combining Signal and Noise - Station Capability
Coupled with noise estimates, we can map out station sensitivity, indicating which regions and what magnitude events we can hope to record. They can be expressed as signal-to-noise ratio (SNR) for a particular event size, or magnitude threshold, if a particular SNR threshold level is specified.
-10.0-9.9-9.8-9.7-9.6-9.5-9.4-9.3-9.2-9.1-9.0-8.9-8.8-8.7-8.6-8.5-8.4-8.3-8.2-8.1-8.0-7.9-7.8-7.7
Log
Ampl
itude
200020012002200320042005200620072008200920102011Date
ABKT/BHZ00 4.0-6.0 Hz
-9.117 +/- 0.473
-11.0
-10.5
-10.0
-9.5
-9.0
-8.5
-8.0
-7.5
-7.0
Dis
plac
emen
t (m
)
YKW3BHZ
MAKZBHZ
ABK31BHZYKW3EHZ
ANMOBHZ00ANMOBHZ10
TX31BHZ
BUR31BHZUQSKBHZ
MK31BHZ
AKTOBHZKLRBHZRAYNBHZHALMLLBHZKSWWHHZKBRSHHZ
PD31BHZ
RAYNBHZ10RANILLBHZCB31BHZ
AFIFBHZ
ELKvbz
KSSSHHZANMOBHZKK31BHZ
FL07SHZHILSHHZ
JNUBHZMALTBHZHIABHZUZMLETBHZ01
BRVKSHZ00MALTSHZKURKBHZ00TUCBHZ00
BRVKBHZBR131BHZBR131BHZASFBHZDUGBHZBGCABHZ
BRVKBHZ00
ZHSFBHZ
KBZBHZNEWBHZ
YNBSHHZSODABHZGARBHZLSZBHZ00LSZBHZ10SNGEBHZ
KIEVBHZ00KIEVBHZNASNBHZLSABHZ
GRMIBHZ
HRABHZYBHBHZ
HIABHZ00HIASHZ10MLRBHZ
LVZBHZ00KBLBHIZ
RAYNBHZ00
CHTHBHZ
FIA0SHZVTSBHZ
ARUBHZTKLBHZHIASHZ
MSDYETBHZ01ABKTSHZ00TPNVBHZ
KBLBHZ
ASAOBHZ
MDJBHZABKTBHZABKTBHZ00AGINETBHZ01CMBBHZ
UOSSBHZ10UOSSBHZ10UOSSBHZ00UOSSBHZ00MEZEBHZ
KCCBHZ
MDJBHZ00AAKBHZJOWBHZ
KNBvbzKNBvbz
GYA0BBHZUSA0BBHZGYA0BHZMDJBHZ10
WUSBHZ
KSJSHHZ
MBARBHZ00
MMA0BBHZ
EILBHZDAMVBHZKYPRETBHZ01
HYBBHZKS31BHZWMQBHZ
MNVBHZ
BJTBHZKSBB+1HHZGNISHZ10
ELKv
MDJSHZ
BJTSHZ
MNVvbz
GNIBHZGNIBHZ00
NV31BHZ
KIVBHZ00GHIRBHZ
BJTBHZ00
PALKBHZ00NILBHZ10QURSHHZ
LACvbz
WMQBHZ00KEVBHZ
DACBHZLACv
WMQBHZ10
KEVBHZ10SIRNETBHZ01
KEVBHZ00BJTSHZ10INCNBHZ10
NILSHZWSARBHZMBARBHZ10
KEVSHZHASSHHZRUWJC1BHZ
YSSBHZ
SSEBHZPALKBHZ10
PFOBHZ
KIVBHZ10TJNBHZ
OBNBHZ
PFOBHZ00
SSESHZQW00HHZNILBHZ
ATDBHZYSSBHZ00
KRBRBHZ
ISPBHZBNDSBHZKBDBHZ
KIVBHZ
INCNBHZ00INCNBHZKEGBHZINUBHZ
HITJC1BHZCMIGBHZINCNSHZTSKBHZ
SHGRBHZSONA0SHZKNBvKNBv
SSEBHZ00QW21EHZSSEBHZ10QW22EHZQW12EHZQW23EHZQW24EHZQW25EHZQW11EHZQW13EHZMNVv
MIBSHZ
UMRSHZ
UNMBHZ
ZALSHZ
Noise Statistics in 1-2 Hz Frequency Band
Seismic Amplitudes
Using information on the earth’s attenuation structure and combining this with source models, one can estimate the amplitudes expected to be observed by recording seismic stations. The observed amplitude A from event i recorded at station j is the product of a source term S, geometrical spreading term G, apparent attenuation term B and site term P.
Aij = S
i * G
ij * B
ij * P
j
where the source term S is formulated in terms of the MDAC source model (Walter and Taylor, 2001)
S = F Mo / (1+(ω/ω
c)2)
where Mo is the seismic moment and the corner frequency ω
c is specified as:
ωc = ((K σ)/M
o)(1/3)
and F and K are constants that are related to the medium properties.
Combining Signal and Noise - Network Capability
Station maps can be combined to form network capability maps. We look at the regional performance of the International Monitoring System (IMS) in Eastern Asia and Western North America.
NOTE: These figures represent regional capability for the stations shown, and therefore do not necessarily reflect the overall levels of the IMS or other networks, which include teleseismic arrivals and additional stations.
-8.8
-8.7
-8.6
-8.5
-8.4
-8.3
-8.2
-8.1
-8.0
-7.9
-7.8
-7.7
-7.6
Log
Ampl
itude
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0Fraction of Year
KEV/BHZ10 1.0-2.0 Hz
-9.0-8.9-8.8-8.7-8.6-8.5-8.4-8.3-8.2-8.1-8.0-7.9-7.8-7.7-7.6-7.5-7.4-7.3-7.2-7.1-7.0-6.9-6.8-6.7-6.6-6.5-6.4-6.3-6.2-6.1-6.0-5.9-5.8-5.7-5.6
Log
Ampl
itude
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0Fraction of Day
ABKT/BHZ00 1.0-2.0 Hz
Crustal Qs
178 316 562 1000 1778Qs
Mantle Qs
178 316 562 1000 1778 3162Qs
Crustal Qp
178 316 562 1000 1778Qp
Mantle Qp
178 562 1778 5623Qp
40˚E 50˚E 60˚E 70˚E 80˚E20˚N
30˚N
40˚N
50˚N
2.5 3.0 3.5 4.0 4.5 5.0 5.5Magnitude
ABKT
Pn 2.0 at station ABKT at threshold level 0.3
40˚E 50˚E 60˚E 70˚E 80˚E20˚N
30˚N
40˚N
50˚N
2.5 3.0 3.5 4.0 4.5 5.0 5.5Magnitude
ABKT
Pn 2.0 at station ABKT at threshold level 0.0
40˚E 50˚E 60˚E 70˚E 80˚E20˚N
30˚N
40˚N
50˚N
-1.0 0.00.3 1.0 2.0 3.0log(Signal-to-Noise Ratio)
ABKT
Pn 2.0 at station ABKT for Mw 4.0 EQ
40˚E 50˚E 60˚E 70˚E 80˚E20˚N
30˚N
40˚N
50˚N
-1.0 0.00.3 1.0 2.0 3.0log(Signal-to-Noise Ratio)
ABKT
Pn 2.0 at station ABKT for Mw 3.5 EQ
110˚E 120˚E 130˚E 140˚E30˚N
40˚N
50˚N
-1.0 0.00.3 1.0 2.0 3.0log(Signal-to-Noise Ratio)
BJTBJTBJTBJTBJTBJT
HIAHIAHIAHIAHIAHIA
JHJJHJJHJJHJJHJJHJ
JKJKJKJKJKJK
JNUJNUJNUJNUJNUJNU
KLRKLRKLRKLRKLRKLR
KS31KS31KS31KS31KS31KS31 MJB9BMJB9BMJB9BMJB9BMJB9BMJB9B
SSESSESSESSESSESSE
USA0BUSA0BUSA0BUSA0BUSA0BUSA0B
YSYSYSYSYSYS
Pn 0.5-6.0 Hz NETWORK for Mw 4.0 EQ
110˚E 120˚E 130˚E 140˚E30˚N
40˚N
50˚N
-1.0 0.00.3 1.0 2.0 3.0log(Signal-to-Noise Ratio)
BJTBJTBJTBJTBJTBJT
HIAHIAHIAHIAHIAHIA
JHJJHJJHJJHJJHJJHJ
JKJKJKJKJKJK
JNUJNUJNUJNUJNUJNU
KLRKLRKLRKLRKLRKLR
KS31KS31KS31KS31KS31KS31 MJB9BMJB9BMJB9BMJB9BMJB9BMJB9B
SSESSESSESSESSESSE
USA0BUSA0BUSA0BUSA0BUSA0BUSA0B
YSYSYSYSYSYS
Pn 0.5-8.0 Hz NETWORK for Mw 3.5 EQ
110˚E 120˚E 130˚E 140˚E30˚N
40˚N
50˚N
-1.0 0.00.3 1.0 2.0 3.0log(Signal-to-Noise Ratio)
BJTBJTBJTBJTBJTBJT
HIAHIAHIAHIAHIAHIA
JHJJHJJHJJHJJHJJHJ
JKJKJKJKJKJK
JNUJNUJNUJNUJNUJNU
KLRKLRKLRKLRKLRKLR
KS31KS31KS31KS31KS31KS31 MJB9BMJB9BMJB9BMJB9BMJB9BMJB9B
SSESSESSESSESSESSE
USA0BUSA0BUSA0BUSA0BUSA0BUSA0B
YSYSYSYSYSYS
Pn 6.0 NETWORK for Mw 3.5 EQ
130˚W 120˚W 110˚W 100˚W
30˚N
40˚N
50˚N
-1.0 0.00.3 1.0 2.0 3.0log(Signal-to-Noise Ratio)
ANMOANMOANMOANMOANMOANMO
BBBBBBBBBBBBBBBBBB
ELKELKELKELKELKELK
NEWNEWNEWNEWNEWNEW
NV31NV31NV31NV31NV31NV31
PD31PD31PD31PD31PD31PD31
PFOPFOPFOPFOPFOPFO
TX31TX31TX31TX31TX31TX31
YBHYBHYBHYBHYBHYBH
Pn 0.5-6.0 Hz NETWORK for Mw 4.0 EQ
130˚W 120˚W 110˚W 100˚W
30˚N
40˚N
50˚N
-1.0 0.00.3 1.0 2.0 3.0log(Signal-to-Noise Ratio)
ANMOANMOANMOANMOANMOANMO
BBBBBBBBBBBBBBBBBB
ELKELKELKELKELKELK
NEWNEWNEWNEWNEWNEW
NV31NV31NV31NV31NV31NV31
PD31PD31PD31PD31PD31PD31
PFOPFOPFOPFOPFOPFO
TX31TX31TX31TX31TX31TX31
YBHYBHYBHYBHYBHYBH
Pn 2.0 NETWORK (3 STA) for Mw 4.0 EQ
130˚W 120˚W 110˚W 100˚W
30˚N
40˚N
50˚N
-1.0 0.00.3 1.0 2.0 3.0log(Signal-to-Noise Ratio)
ANMOANMOANMOANMOANMOANMO
BBBBBBBBBBBBBBBBBB
ELKELKELKELKELKELK
NEWNEWNEWNEWNEWNEW
NV31NV31NV31NV31NV31NV31
PD31PD31PD31PD31PD31PD31
PFOPFOPFOPFOPFOPFO
TX31TX31TX31TX31TX31TX31
YBHYBHYBHYBHYBHYBH
Pn 2.0 NETWORK (4 STA) for Mw 4.0 EQ
110˚E 120˚E 130˚E 140˚E30˚N
40˚N
50˚N
-10.0-9.5-9.0-8.5-8.0-7.5-7.0-6.5-6.0-5.5-5.0log(Signal)
USA0B
Pn 2.0 at station USA0B for Mw 4.0 EQ
130˚W 120˚W 110˚W 100˚W 90˚W
30˚N
40˚N
50˚N
-1.0 0.00.3 1.0 2.0 3.0log(Signal-to-Noise Ratio)
ELK
Lg 4.0 at station ELK for Mw 4.0 EQ
130˚W 120˚W 110˚W 100˚W 90˚W
30˚N
40˚N
50˚N
-1.0 0.00.3 1.0 2.0 3.0log(Signal-to-Noise Ratio)
ELK
Lg coda 4.0 at station ELK for Mw 4.0 EQ
110˚E 120˚E 130˚E 140˚E30˚N
40˚N
50˚N
-1.0 0.00.3 1.0 2.0 3.0log(Signal-to-Noise Ratio)
BJTBJTBJTBJTBJTBJTBJTBJTBJTBJTBJT
HIAHIAHIAHIAHIAHIAHIAHIAHIAHIAHIA
JHJJHJJHJJHJJHJJHJJHJJHJJHJJHJJHJ
JKJKJKJKJKJKJKJKJKJKJK
JNUJNUJNUJNUJNUJNUJNUJNUJNUJNUJNU
KLRKLRKLRKLRKLRKLRKLRKLRKLRKLRKLR
KS31KS31KS31KS31KS31KS31KS31KS31KS31KS31KS31 MJB9BMJB9BMJB9BMJB9BMJB9BMJB9BMJB9BMJB9BMJB9BMJB9BMJB9B
SSESSESSESSESSESSESSESSESSESSESSE
USA0BUSA0BUSA0BUSA0BUSA0BUSA0BUSA0BUSA0BUSA0BUSA0BUSA0B
YSYSYSYSYSYSYSYSYSYSYS
Sn 6.0 NETWORK for Mw 3.0 EQ
110˚E 120˚E 130˚E 140˚E30˚N
40˚N
50˚N
-1.0 0.00.3 1.0 2.0 3.0log(Signal-to-Noise Ratio)
BJTBJTBJTBJTBJTBJTBJTBJTBJTBJTBJT
HIAHIAHIAHIAHIAHIAHIAHIAHIAHIAHIA
JHJJHJJHJJHJJHJJHJJHJJHJJHJJHJJHJ
JKJKJKJKJKJKJKJKJKJKJK
JNUJNUJNUJNUJNUJNUJNUJNUJNUJNUJNU
KLRKLRKLRKLRKLRKLRKLRKLRKLRKLRKLR
KS31KS31KS31KS31KS31KS31KS31KS31KS31KS31KS31 MJB9BMJB9BMJB9BMJB9BMJB9BMJB9BMJB9BMJB9BMJB9BMJB9BMJB9B
SSESSESSESSESSESSESSESSESSESSESSE
USA0BUSA0BUSA0BUSA0BUSA0BUSA0BUSA0BUSA0BUSA0BUSA0BUSA0B
YSYSYSYSYSYSYSYSYSYSYS
Lg 6.0 NETWORK for Mw 3.0 EQ
This work was prepared under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344. The work is sponsored by the U.S. Department of State Contributions-in-Kind (CiK). The views expressed here do not necessarily reflect the views of the United States Government, the United States Department of Energy, National Nuclear Security Administration, the United States Department of State, or the Lawrence Livermore National Laboratory. This is LLNL contribution LLNL-POST-671204.