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.