![](media/image1.png){width="1.75in" height="0.6416666666666667in"}

**An Assessment of the High-gain Streckeisen STS2 Seismometer for
Routine Earthquake Monitoring in the United States**

By D. E. McNamara, R.P. Buland and H.M. Benz

Report Series XXXXXXX

U.S. Department of the Interior

U.S. Geological Survey

U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

P. Patrick Leahy, Acting Director

U.S. Geological Survey, Reston, Virginia 200x\
Revised and reprinted: 200x

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# Contents {#contents .TOCHeading1}

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References Cited [**Error! Bookmark not
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Glossary [**Error! Bookmark not defined.**](#__RefHeading___Toc95029652)

# Figures {#figures .TOCHeading1}

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the (*C*) MultipartFigCap style. [**Error! Bookmark not
defined.**](#__RefHeading___Toc81886779)

# Tables {#tables .TOCHeading1}

1\. This is a table title. [**Error! Bookmark not
defined.**](#__RefHeading___Toc81886945)

# Conversion Factors {#conversion-factors .TOCHeading1}

## Inch/Pound to SI {#inchpound-to-si .TOCHeading2}

  ------------------------- -------------------- -------------------------
  Multiply                  By                   To obtain

  Length                                         

  inch (in.)                2.54                 centimeter (cm)

  inch (in.)                25.4                 millimeter (mm)

  foot (ft)                 0.3048               meter (m)

  mile (mi)                 1.609                kilometer (km)

  mile, nautical (nmi)      1.852                kilometer (km)

  yard (yd)                 0.9144               meter (m)

  Area                                           

  acre                      4,047                square meter (m^2^)

  acre                      0.4047               hectare (ha)

  acre                      0.4047               square hectometer (hm^2^)

  acre                      0.004047             square kilometer (km^2^)

  square foot (ft^2^)       929.0                square centimeter (cm^2^)

  square foot (ft^2^)       0.09290              square meter (m^2^)

  square inch (in^2^)       6.452                square centimeter (cm^2^)

  section (640 acres or 1   259.0                square hectometer (hm^2^)
  square mile)                                   

  square mile (mi^2^)       259.0                hectare (ha)

  square mile (mi^2^)       2.590                square kilometer (km^2^)

  Volume                                         

  barrel (bbl),             0.1590               cubic meter (m^3^)
  (petroleum,\                                   
  1 barrel=42 gal)                               

  ounce, fluid (fl. oz)     0.02957              liter (L)

  pint (pt)                 0.4732               liter (L)

  quart (qt)                0.9464               liter (L)

  gallon (gal)              3.785                liter (L)

  gallon (gal)              0.003785             cubic meter (m^3^)

  gallon (gal)              3.785                cubic decimeter (dm^3^)

  million gallons (Mgal)    3,785                cubic meter (m^3^)

  cubic inch (in^3^)        16.39                cubic centimeter (cm^3^)

  cubic inch (in^3^)        0.01639              cubic decimeter (dm^3^)

  cubic inch (in^3^)        0.01639              liter (L)

  cubic foot (ft^3^)        28.32                cubic decimeter (dm^3^)

  cubic foot (ft^3^)        0.02832              cubic meter (m^3^)

  cubic yard (yd^3^)        0.7646               cubic meter (m^3^)

  cubic mile (mi^3^)        4.168                cubic kilometer (km^3^)

  acre-foot (acre-ft)       1,233                cubic meter (m^3^)

  acre-foot (acre-ft)       0.001233             cubic hectometer (hm^3^)

  Flow rate                                      

  acre-foot per day         0.01427              cubic meter per second
  (acre-ft/d)                                    (m^3^/s)

  acre-foot per year        1,233                cubic meter per year
  (acre-ft/yr)                                   (m^3^/yr)

  acre-foot per year        0.001233             cubic hectometer per year
  (acre-ft/yr)                                   (hm^3^/yr)

  foot per second (ft/s)    0.3048               meter per second (m/s)

  foot per minute (ft/min)  0.3048               meter per minute (m/min)

  foot per hour (ft/hr)     0.3048               meter per hour (m/hr)

  foot per day (ft/d)       0.3048               meter per day (m/d)

  foot per year (ft/yr)     0.3048               meter per year (m/yr)

  cubic foot per second     0.02832              cubic meter per second
  (ft^3^/s)                                      (m^3^/s)

  cubic foot per second per 0.01093              cubic meter per second
  square\                                        per square kilometer
  mile \[(ft^3^/s)/mi^2^\]                       \[(m^3^/s)/km^2^\]

  cubic foot per day        0.02832              cubic meter per day
  (ft^3^/d)                                      (m^3^/d)

  gallon per minute         0.06309              liter per second (L/s)
  (gal/min)                                      

  gallon per day (gal/d)    0.003785             cubic meter per day
                                                 (m^3^/d)

  gallon per day per square 0.001461             cubic meter per day per
  mile\                                          square\
  \[(gal/d)/mi^2^\]                              kilometer
                                                 \[(m^3^/d)/km^2^\]

  million gallons per day   0.04381              cubic meter per second
  (Mgal/d)                                       (m^3^/s)

  million gallons per day   1,461                cubic meter per day per
  per square mile                                square\
  \[(Mgal/d)/mi^2^\]                             kilometer
                                                 \[(m^3^/d)/km^2^\]

  inch per hour (in/h)      0 .0254              meter per hour (m/h)

  inch per year (in/yr)     25.4                 millimeter per year
                                                 (mm/yr)

  mile per hour (mi/h)      1.609                kilometer per hour (km/h)

  Mass                                           

  ounce, avoirdupois (oz)   28.35                gram (g)

  pound, avoirdupois (lb)   0.4536               kilogram (kg)

  ton, short (2,000 lb)     0.9072               megagram (Mg)

  ton, long (2,240 lb)      1.016                megagram (Mg)

  ton per day (ton/d)       0.9072               metric ton per day

  ton per day (ton/d)       0.9072               megagram per day (Mg/d)

  ton per day per square    0.3503               megagram per day per
  mile\                                          square\
  \[(ton/d)/mi^2^\]                              kilometer
                                                 \[(Mg/d)/km^2^\]

  ton per year (ton/yr)     0.9072               megagram per year (Mg/yr)

  ton per year (ton/yr)     0.9072               metric ton per year

  Pressure                                       

  atmosphere, standard      101.3                kilopascal (kPa)
  (atm)                                          

  bar                       100                  kilopascal (kPa)

  inch of mercury at 60ºF   3.377                kilopascal (kPa)
  (in Hg)                                        

  pound-force per square    6.895                kilopascal (kPa)
  inch\                                          
  (lbf/in^2^)                                    

  pound per square foot     0.04788              kilopascal (kPa)
  (lb/ft^2^)                                     

  pound per square inch     6.895                kilopascal (kPa)
  (lb/in^2^)                                     

  Density                                        

  pound per cubic foot      16.02                kilogram per cubic meter
  (lb/ft^3^)                                     (kg/m^3^)

  pound per cubic foot      0.01602              gram per cubic centimeter
  (lb/ft^3^)                                     (g/cm^3^)

  Energy                                         

  kilowatthour (kWh)        3,600,000            joule (J)

  Radioactivity                                  

  picocurie per liter       0.037                becquerel per liter
  (pCi/L)                                        (Bq/L)

  Specific capacity                              

  gallon per minute per     0.2070               liter per second per
  foot\                                          meter \[(L/s)/m\]
  \[(gal/min)/ft)\]                              

  Hydraulic conductivity                         

  foot per day (ft/d)       0.3048               meter per day (m/d)

  Hydraulic gradient                             

  foot per mile (ft/mi)     0.1894               meter per kilometer
                                                 (m/km)

  Transmissivity\*                               

  foot squared per day      0.09290              meter squared per day
  (ft^2^/d)                                      (m^2^/d)

  Application rate                               

  pounds per acre per year\ 1.121                kilograms per hectare per
  \[(lb/acre)/yr\]                               year\
                                                 \[(kg/ha)/yr\]

  Leakance                                       

  foot per day per foot     1                    meter per day per meter
  \[(ft/d)/ft\]                                  

  inch per year per foot    83.33                millimeter per year per
  \[(in/yr)/ft\]                                 meter\
                                                 \[(mm/yr)/m\]
  ------------------------- -------------------- -------------------------

Temperature in degrees Celsius (°C) may be converted to degrees
Fahrenheit (°F) as follows:

°F=(1.8×°C)+32

Temperature in degrees Fahrenheit (°F) may be converted to degrees
Celsius (°C) as follows:

°C=(°F-32)/1.8

Vertical coordinate information is referenced to the insert datum name
(and abbreviation) here for instance, "North American Vertical Datum of
1988 (NAVD 88)."

Horizontal coordinate information is referenced to the insert datum name
(and abbreviation) here for instance, "North American Datum of 1983 (NAD
83)."

Altitude, as used in this report, refers to distance above the vertical
datum.

\*Transmissivity: The standard unit for transmissivity is cubic foot per
day per square foot times foot of aquifer thickness
\[(ft^3^/d)/ft^2^\]ft. In this report, the mathematically reduced form,
foot squared per day (ft^2^/d), is used for convenience.

Specific conductance is given in microsiemens per centimeter at 25
degrees Celsius (µS/cm at 25 °C).

Concentrations of chemical constituents in water are given either in
milligrams per liter (mg/L) or micrograms per liter (µg/L).

NOTE TO USGS USERS: Use of hectare (ha) as an alternative name for
square hectometer (hm^2^) is restricted to the measurement of small land
or water areas. Use of liter (L) as a special name for cubic decimeter
(dm^3^) is restricted to the measurement of liquids and gases. No prefix
other than milli should be used with liter. Metric ton (t) as a name for
megagram (Mg) should be restricted to commercial usage, and no prefixes
should be used with it.

## SI to Inch/Pound {#si-to-inchpound .TOCHeading2}

  ------------------------- ------------------- -------------------------
  Multiply                  By                  To obtain

  Length                                        

  centimeter (cm)           0.3937              inch (in.)

  millimeter (mm)           0.03937             inch (in.)

  meter (m)                 3.281               foot (ft)

  kilometer (km)            0.6214              mile (mi)

  kilometer (km)            0.5400              mile, nautical (nmi)

  meter (m)                 1.094               yard (yd)

  Area                                          

  square meter (m^2^)       0.0002471           acre

  hectare (ha)              2.471               acre

  square hectometer (hm^2^) 2.471               acre

  square kilometer (km^2^)  247.1               acre

  square centimeter (cm^2^) 0.001076            square foot (ft^2^)

  square meter (m^2^)       10.76               square foot (ft^2^)

  square centimeter (cm^2^) 0.1550              square inch (ft^2^)

  square hectometer (hm^2^) 0.003861            section (640 acres or 1
                                                square mile)

  hectare (ha)              0.003861            square mile (mi^2^)

  square kilometer (km^2^)  0.3861              square mile (mi^2^)

  Volume                                        

  cubic meter (m^3^)        6.290               barrel (petroleum, 1
                                                barrel = 42 gal)

  liter (L)                 33.82               ounce, fluid (fl. oz)

  liter (L)                 2.113               pint (pt)

  liter (L)                 1.057               quart (qt)

  liter (L)                 0.2642              gallon (gal)

  cubic meter (m^3^)        264.2               gallon (gal)

  cubic decimeter (dm^3^)   0.2642              gallon (gal)

  cubic meter (m^3^)        0.0002642           million gallons (Mgal)

  cubic centimeter (cm^3^)  0.06102             cubic inch (in^3^)

  cubic decimeter (dm^3^)   61.02               cubic inch (in^3^)

  liter (L)                 61.02               cubic inch (in^3^)

  cubic decimeter (dm^3^)   0.03531             cubic foot (ft^3^)

  cubic meter (m^3^)        35.31               cubic foot (ft^3^)

  cubic meter (m^3^)        1.308               cubic yard (yd^3^)

  cubic kilometer (km^3^)   0.2399              cubic mile (mi^3^)

  cubic meter (m^3^)        0.0008107           acre-foot (acre-ft)

  cubic hectometer (hm^3^)  810.7               acre-foot (acre-ft)

  Flow rate                                     

  cubic meter per second    70.07               acre-foot per day
  (m^3^/s)                                      (acre-ft/d)

  cubic meter per year      0.000811            acre-foot per year
  (m^3^/yr)                                     (acre-ft/yr)

  cubic hectometer per year 811.03              acre-foot per year
  (hm^3^/yr)                                    (acre-ft/yr)

  meter per second (m/s)    3.281               foot per second (ft/s)

  meter per minute (m/min)  3.281               foot per minute (ft/min)

  meter per hour (m/hr)     3.281               foot per hour (ft/hr)

  meter per day (m/d)       3.281               foot per day (ft/d)

  meter per year (m/yr)     3.281               foot per year ft/yr)

  cubic meter per second    35.31               cubic foot per second
  (m^3^/s)                                      (ft^3^/s)

  cubic meter per second    91.49               cubic foot per second per
  per square kilometer                          square\
  \[(m^3^/s)/km^2^\]                            mile \[(ft^3^/s)/mi^2^\]

  cubic meter per day       35.31               cubic foot per day
  (m^3^/d)                                      (ft^3^/d)

  liter per second (L/s)    15.85               gallon per minute
                                                (gal/min)

  cubic meter per day       264.2               gallon per day (gal/d)
  (m^3^/d)                                      

  cubic meter per day per   684.28              gallon per day per square
  square\                                       mile\
  kilometer                                     \[(gal/d)/mi^2^\]
  \[(m^3^/d)/km^2^\]                            

  cubic meter per second    22.83               million gallons per day
  (m^3^/s)                                      (Mgal/d)

  cubic meter per day per   0.0006844           million gallons per day
  square\                                       per square mile
  kilometer                                     \[(Mgal/d)/mi^2^\]
  \[(m^3^/d)/km^2^\]                            

  cubic meter per hour      39.37               inch per hour (in/h)
  (m^3^/h)                                      

  millimeter per year       0.03937             inch per year (in/yr)
  (mm/yr)                                       

  kilometer per hour (km/h) 0.6214              mile per hour (mi/h)

  Mass                                          

  gram (g)                  0.03527             ounce, avoirdupois (oz)

  kilogram (kg)             2.205               pound avoirdupois (lb)

  megagram (Mg)             1.102               ton, short (2,000 lb)

  megagram (Mg)             0.9842              ton, long (2,240 lb)

  metric ton per day        1.102               ton per day (ton/d)

  megagram per day (Mg/d)   1.102               ton per day (ton/d)

  megagram per day per      2.8547              ton per day per square
  square\                                       mile\
  kilometer                                     \[(ton/d)/mi^2^\]
  \[(Mg/d)/km^2^\]                              

  megagram per year (Mg/yr) 1.102               ton per year (ton/yr)

  metric ton per year       1.102               ton per year (ton/yr)

  Pressure                                      

  kilopascal (kPa)          0.009869            atmosphere, standard
                                                (atm)

  kilopascal (kPa)          0.01                bar

  kilopascal (kPa)          0.2961              inch of mercury at 60°F
                                                (in Hg)

  kilopascal (kPa)          0.1450              pound-force per inch
                                                (lbf/in)

  kilopascal (kPa)          20.88               pound per square foot
                                                (lb/ft^2^)

  kilopascal (kPa)          0.1450              pound per square inch
                                                (lb/ft^2^)

  Density                                       

  kilogram per cubic meter  0.06242             pound per cubic foot
  (kg/m^3^)                                     (lb/ft^3^)

  gram per cubic centimeter 62.4220             pound per cubic foot
  (g/cm^3^)                                     (lb/ft^3^)

  Energy                                        

  joule (J)                 0.0000002           kilowatthour (kWh)

  Radioactivity                                 

  becquerel per liter       27.027              picocurie per liter
  (Bq/L)                                        (pCi/L)

  Specific capacity                             

  liter per second per      4.831               gallon per minute per
  meter \[(L/s)/m\]                             foot \[(gal/min)/ft\]

  Hydraulic conductivity                        

  meter per day (m/d)       3.281               foot per day (ft/d)

  Hydraulic gradient                            

  meter per kilometer       5.27983             foot per mile (ft/mi)
  (m/km)                                        

  Transmissivity\*                              

  meter squared per day     10.76               foot squared per day
  (m^2^/d)                                      (ft^2^/d)

  Application rate                              

  kilograms per hectare per 0.8921              pounds per acre per year\
  year\                                         \[(lb/acre)/yr\]
  \[(kg/ha)/yr\]                                

  Leakance                                      

  meter per day per meter   1                   foot per day per foot
  \[(m/d)/m\]                                   \[(ft/d)/ft\]

  millimeter per year per   0.012               inch per year per foot
  meter\                                        \[(in/yr)/ft\]
  \[(mm/yr)/m\]                                 
  ------------------------- ------------------- -------------------------

Temperature in degrees Celsius (°C) may be converted to degrees
Fahrenheit (°F) as follows:

°F=(1.8×°C)+32

Temperature in degrees Fahrenheit (°F) may be converted to degrees
Celsius (°C) as follows:

°C=(°F-32)/1.8

Vertical coordinate information is referenced to the insert datum name
(and abbreviation) here, for instance, "North American Vertical Datum of
1988 (NAVD 88)"

Horizontal coordinate information is referenced to the insert datum name
(and abbreviation) here, for instance, "North American Datum of 1983
(NAD 83)"

Altitude, as used in this report, refers to distance above the vertical
datum.

\*Transmissivity: The standard unit for transmissivity is cubic foot per
day per square foot times foot of aquifer thickness
\[(ft^3^/d)/ft^2^\]ft. In this report, the mathematically reduced form,
foot squared per day (ft^2^/d), is used for convenience.

Specific conductance is given in microsiemens per centimeter at 25
degrees Celsius (µS/cm at 25°C).

Concentrations of chemical constituents in water are given either in
milligrams per liter (mg/L) or micrograms per liter (µg/L).

NOTE TO USGS USERS: Use of hectare (ha) as an alternative name for
square hectometer (hm^2^) is restricted to the measurement of small land
or water areas. Use of liter (L) as a special name for cubic decimeter
(dm^3^) is restricted to the measurement of liquids and gases. No prefix
other than milli should be used with liter. Metric ton (t) as a name for
megagram (Mg) should be restricted to commercial usage, and no prefixes
should be used with it.

**An Assessment of the High-gain Streckeisen STS2 Seismometer for
Routine Earthquake Monitoring in the United States**

By D. E. McNamara, R.P. Buland, and H.M. Benz[^1]

# Abstract 

**Objective**. In this document, we report the results of a study to
determine if the Streckeisen STS2 high-gain seismometer is appropriate
for use by the United States Geological Survey's (USGS) Advanced
National Seismic System (ANSS) for routine earthquake monitoring in the
United States (US).

**Issue**. At issue is whether the high-gain STS2, with a sensitivity of
20,000 volts/meter/sec, can produce onscale recordings of earthquake
activity within the continental US, or whether the low-gain STS2, with a
sensitivity of 1500 volts/meter/sec, is more appropriate for earthquake
monitoring due to the relatively lower input velocity required for
clipping the recording system. The test ANSS backbone station
configuration, considered in this study, consists of an STS2 broadband
seismometer coupled to a Quanterra Q330 digitizer. The Q330 has a
channel sensitivity of 4.19e5 counts/volt and a clip level of 8.38e6 =
8388608 counts (2e23) (20 volts). Therefore, an input ground velocity of
only 0.001 m/sec will clip the high-gain system while an input ground
velocity of 0.013 m/sec, a factor of 13 larger, is required to clip the
lower-gain configuration.

**Methods**. In this report, we use three different methods to examine
the levels of input ground velocity expected during routine earthquake
monitoring within the continental US. These methods include:

1.  Computing peak ground velocity (PGV) expected at each ANSS backbone
    station from the USGS's 10 percent probability of exceedance in 30
    years 1Hz spectral acceleration maps (fig. 1).

2.  Modeling the amplitude of PGV at regional distances using Brune
    source scaling (fig. 2).

3.  Analysis of the September 2004, M6 Parkfield earthquake at four
    broadband seismic stations within 1000km of the epicenter (figs. 2
    and 3).

**Recommendation**: Based on the analysis of the three methods discussed
above, it is our recommendation that the low-gain STS2 is more
appropriate for routine earthquake monitoring in the US. Method 1
indicates that if the high-gain configuration is used at all ANSS
backbone stations, all can be expected to clip given the ground-shaking
levels expected in the next 30 years. Methods 2 and 3 indicate that an
M6 will clip stations within approximately 875 km of the epicenter. The
high-gain STS2 is more useful for recording teleseismic events on a
global scale but not suitable for onscale recording of moderate to large
earthquakes within the continental US.

**Methods:**

**I. PGV computed from 1Hz Spectral Acceleration Map.**

# In this analysis we use the 1 Hz spectral acceleration 10% probability of exceedance in 30 years to calculate the expected PGV at each ANSS backbone station within the continental US (Frankel et al., 2002). The method includes the following procedures:

1.  For each ANSS station, determine *%g* from the 1 Hz spectral
    acceleration map (fig. 1) and convert to *g* (*g = 0.01\* %g*) where
    *1g=980cm/s/s*.

2.  Compute PGV in m/sec after (Newmark and Hall, 1982) where

> *PGV = 594.8 \* g / (2\*).*

3.  Compare PGV to clipping velocity of low and high-gain recording
    systems.

Results from this analysis are summarized in table 1 and in figure 1.
All high-gain STS2's will clip the Q330 digitizer given the input PGV
computed from the 10 percent probability of exceedance spectral
acceleration in the next 30 years. In contrast, 70 percent of the
low-gain STS2's will clip in the regions with the highest expected input
ground velocity. Stations in the midcontinent are not expected to clip
(fig. 1). The high level of clipped stations for the low and high gain
STS2 seismometers indicate the importance of colocated low gain
accelerometers if onscale recording of all large motion is desired.

# II. Brune Source Modeling

In this analysis, we calculate expected shear-wave amplitude using the
source scaling models of Brune (1970) and Brune (1971) for a range of
distances (25-1200 km) and magnitudes (M5-7). We then compare the
modeled amplitude to the velocity required to clip the high and low gain
recording systems. (fig. 2). The method includes the following
procedures.

1\. For each Mw, determine Mo from: Mw = 0.667 log(Mo) -- 10.7
(*Kanimori,* 1977).

2\. For each Mo, determine fault dimension from: Mo = 2.29σr^3^ dyne-cm

(*Brune* 1970, 1971) where σ = 1.0\*10^8^ effective stress.

3\. For each fault dimension, determine source corner frequency from:

> $r = \frac{2\text{.}\text{21}\beta}{2p\text{fc}}$ fault dimension in
> cm *(Brune* 1970, 1971*).*
>
> where *β* = shear wave velocity = 3.5km/s

*fc* = source corner frequency

4\. Find angular frequency (*fm*), by bisection, where Brune source
spectrum is a maximum given ANSS short-period detection filters (0.5-12
Hz).

5\. For each source-receiver distance (from 25-1100 km), calculate
Shear-wave PGV amplitude (*As*) in m/sec from:

$\text{As} = \frac{\text{Mo}}{4\text{mβ}} \cdot \frac{\text{fmfc}^{2}}{\text{fm}^{2}} + \frac{\text{fc}^{2}}{D}$
*(Brune* 1970, 1971*).*

where *μ* = rigidity,

*fc* = source corner frequency,

*fm* = effective frequency where amplitude is maximum,

*β* = shear-wave velocity (3.5km/s), and

** = source-receiver distance.

5\. Apply attenuation to Shear-wave amplitude (As).

$\text{As} = \frac{\text{As}}{D^{g}} \cdot e^{\frac{- p\text{fm}D}{Q\beta}}$

where *γ* = geometric spreading (0.5)

*Q* = Quality factor.

Northern California (Erickson et al. 2004).

*Q* = 105*fm* ^0.67^

6\. Multiply the modeled amplitude by the total sensitivity of the
high-gain recording system (8.38e9 counts/m/s) and plot corrected PGV as
a function of epicentral distance.

Results from this analysis are shown in figure 2 along with the input
clipping velocities for the high and low-gain systems. From figure 2, we
see that an earthquake with a magnitude of 6.0 will clip the high-gain
system at distances less than about 875 km while the low-gain system
will clip at distances less than 150 km. A magnitude 5.0 will clip the
high-gain system at distances less than 175 km.

# III. M6.0 Parkfield Earthquake, September 2004

To verify the amplitude modeling results calculated in Method II we
analyzed the amplitudes of the September 2004, M6 Parkfield earthquake
at four broadband seismic stations within 1100 km of the epicenter. Four
stations that cooperate with the ANSS from the US, BRK and IU networks
were used in the analysis. In each case, the M6.0 Parkfield earthquake
did not clip any of the broadband stations. The stations used in the
analysis include:

HOPS: Hopland, Mendicino County California. BRK network.

Digitizer: Quanterra Q380 recording at 20 samples/second.

> seismometer : STS1.

COR: Corvallis Oregon, US/IU network.

Digitizer: Quanterra Q380 recording at 20 samples/second.

> Seismometer: STS1(sens 2.51e3 counts/volt)

WDC: Whiskeytown Dam, California, US/BRK network.

Digitizer: Quanterra Q380 recordinga t 20 samples/second.

> Seismometer: Low-gain STS2 (sens 1500 counts/volt).

MOD: Modoc County California, BRK network.

Digitizer: Quanterra QX-80 recording at 20 samples/second.

> Seismometer: STS1 (sens 2240 counts/volt).

The individual station instrument responses (Appendix 1) were
deconvolved from the data and converted to displacement. We then
convolved the data from each station with total response of the Q330 and
high-gain STS2 (Appendix 1). For each station, peak amplitude (PGV) was
measured from the largest arrivals on the vertical component of motion
(BHZ), which at regional distances is dominated the multiply reflected
crustal shear-wave, *Lg*. PGV is then plotted as a function of
epicentral distance (fig. 2) (Table 2).

From figure 2, it is apparent that the three stations closest to the
Parkfield earthquake (HOPS, WDC, MOD) would have clipped if the
high-gain recording systems were in use. In contrast, the stations did
not actually clip with their current instrumentation and would not have
clipped if the low-gain STS2 were deployed (fig. 2). Station COR, at
1003 km, would not have clipped either the low or high-gain system.
Figure 3 shows the amplitude of the Parkfield M6.0 recorded at MOD at
667 km for three different instrumentation configurations. MOD currently
has an STS1 (black line, fig. 3) and did not clip on the Parkfield
earthquake. Figure 3 also demonstrates that a high-gain STS2 recording
system would have been clipped by the Parkfield earthquake at MOD at a
distance of 667 km.

#### Conclusions

Based on the results from this analysis, it is apparent that the
high-gain STS2 is not optimal for routine earthquake monitoring in the
US. The gain level is sufficiently high that moderate size (M6.0)
earthquakes would clip the Quanterra Q330 digitizer at distances less
than 875 km. This is unacceptable if we hope to record these events
onscale. Instead, the high-gain STS2 is more appropriate for remote
seismic stations where weaker ground motion is expected.

# 

# 

# 

# References

Brune, J., 1970, Tectonic stress and the spectra of seismic shear waves
from earthquakes, J. Geophys. Res., 75, 4997-5009.

Brune, J., 1971, Correction, J. Geophys. Res., 76, 5002.

Erickson, D., D. McNamara, H. Benz, 2004, Frequency-dependent Lg Q
within the Continental United States, *Seism. Soc. Am. Bull*, 94,
1630-1643.

Frankel, A., Petersen, M., Mueller, C., Haller, K., Wheeler, R.,
Leyendecker, E., Wesson, R., Harmsen, S., Cramer, C., Perkins, D., and
Rukstales, K., 2002, Documentation for the 2002 update of the national
seismic hazard maps, U.S. Geological Survey Open-File Report 02-420, 39
pages.

Kanimori, 1977, The energy release in great earthquakes, J. Geophys.
Res, 82, 2881-2987.

Newmark, N.M. and Hall, W.J., 1982, \"Earthquake Spectra and Design\"
EERI monograph.

**Table 1. Percent Clip for standard and high-gain STS2 from Method I.**

**Sta latitude longitude %g g PGV SG %clip HG %clip**

(m/s)

AAM 42.300999 -83.656998 1.330970 0.013310 0.0125997 0.944757 12.6018

ACSO 40.231998 -82.983002 1.736430 0.017364 0.016438 1.23256 16.4407

AHID 42.764999 -111.099998 13.802000 0.138020 0.130657 9.79702 130.679

ANMO 34.945999 -106.457001 4.496410 0.044964 0.0425654 3.19167 42.5725

BINY 42.199001 -75.986000 1.559670 0.015597 0.0147647 1.10709 14.7671

BLA 37.210999 -80.420998 2.192460 0.021925 0.020755 1.55626 20.7584

BLO 39.172001 -86.522003 2.566570 0.025666 0.0242965 1.82182 24.3006

BMN 40.431000 -117.222000 8.432590 0.084326 0.0798274 5.98567 79.8407

BOZ 45.599998 -111.633003 9.916620 0.099166 0.093876 7.03907 93.8916

BW06 42.778000 -109.556000 4.586710 0.045867 0.0434202 3.25577 43.4275

CBKS 38.813999 -99.737000 1.145350 0.011454 0.0108425 0.812999 10.8443

CBN 38.205002 -77.373001 1.408630 0.014086 0.0133349 0.999882 13.3371

CCM 38.056000 -91.245003 3.163960 0.031640 0.0299517 2.24586 29.9567

CMB 38.035000 -120.385002 9.530080 0.095301 0.0902169 6.7647 90.2318

COR 44.585999 -123.303001 9.505110 0.095051 0.0899805 6.74697 89.9954

DAC 36.277000 -117.594002 16.641701 0.166417 0.157539 11.8127 157.565

DUG 40.195999 -112.816002 5.698430 0.056984 0.0539444 4.04489 53.9533

DWPF 28.110001 -81.432999 0.653747 0.006537 0.00618872 0.464047 6.18975

ELK 40.744999 -115.238998 4.964200 0.049642 0.0469938 3.52372 47.0016

EYMN 47.945999 -91.495003 0.310897 0.003109 0.00294312 0.220683 2.94361

GOGA 33.410999 -83.467003 2.422660 0.024227 0.0229342 1.71967 22.938

HAWA 46.393002 -119.532997 5.147710 0.051477 0.048731 3.65398 48.7391

HKT 29.950001 -95.833000 0.816093 0.008161 0.00772557 0.579284 7.72685

HLID 43.561001 -114.418999 5.659060 0.056591 0.0535717 4.01695 53.5806

HOPS 38.993999 -123.071999 36.925400 0.369254 0.349556 26.2106 349.614

HRV 42.506001 -71.557999 1.748700 0.017487 0.0165541 1.24127 16.5569

HWUT 41.606998 -111.565002 9.699410 0.096994 0.0918198 6.88489 91.835

ISCO 39.799999 -105.612999 1.654140 0.016541 0.015659 1.17415 15.6616

JCT 30.479000 -99.802002 0.503462 0.005035 0.00476604 0.35737 4.76683

JFWS 42.914001 -90.248001 1.112710 0.011127 0.0105335 0.78983 10.5353

KNB 37.016998 -112.821999 4.696350 0.046964 0.0444582 3.33359 44.4655

**Sta latitude longitude %g g PGV SG %clip HG %clip**

LBNH 44.240002 -71.926003 2.280530 0.022805 0.0215887 1.61878 21.5923

LKWY 44.564999 -110.400002 12.156100 0.121561 0.115076 8.62871 115.095

LRAL 33.035000 -86.998001 2.224120 0.022241 0.0210547 1.57874 21.0582

LSCT 41.678001 -73.223999 1.604300 0.016043 0.0151872 1.13877 15.1897

LTX 29.334000 -103.667000 2.222410 0.022224 0.0210385 1.57752 21.042

MCWV 39.658001 -79.846001 1.584410 0.015844 0.0149989 1.12465 15.0014

MIAR 34.546001 -93.572998 2.096850 0.020968 0.0198499 1.4884 19.8532

MNV 38.432999 -118.153000 17.172800 0.171728 0.162567 12.1897 162.594

MOD 41.903000 -120.306000 8.412420 0.084124 0.0796365 5.97135 79.6497

MVU 38.505001 -112.210999 7.899620 0.078996 0.074782 5.60736 74.7944

MYNC 35.074001 -84.127998 3.033970 0.030340 0.0287212 2.15359 28.726

NCB 43.971001 -74.223999 2.356310 0.023563 0.0223061 1.67257 22.3098

NEW 48.263000 -117.120003 3.619540 0.036195 0.0342645 2.56924 34.2702

NHSC 33.106998 -80.178001 3.245180 0.032452 0.0307206 2.30351 30.7257

OCWA 47.749001 -124.178001 16.503599 0.165036 0.156232 11.7147 156.258

OXF 34.512001 -89.408997 3.180920 0.031809 0.0301123 2.2579 30.1173

PAS 34.147999 -118.171997 37.812199 0.378122 0.357951 26.8401 358.01

PFO 33.609001 -116.455002 33.764099 0.337641 0.319629 23.9666 319.682

PLAL 34.981998 -88.075996 3.189070 0.031891 0.0301894 2.26368 30.1945

RSSD 44.119999 -104.036003 1.247570 0.012476 0.0118102 0.885558 11.8121

SAO 36.764999 -121.445000 43.401501 0.434015 0.410862 30.8075 410.93

SDCO 37.745998 -105.500999 2.562140 0.025621 0.0242546 1.81867 24.2586

SLM 38.636002 -90.236000 3.590330 0.035903 0.033988 2.54851 33.9936

SSPA 40.636002 -77.888000 1.393160 0.013932 0.0131884 0.988901 13.1906

TPH 38.075001 -117.223000 9.866430 0.098664 0.0934009 7.00345 93.4164

TPNV 36.948002 -116.249001 8.793650 0.087936 0.0832454 6.24196 83.2592

TUC 32.310001 -110.783997 2.316950 0.023170 0.0219335 1.64463 21.9371

WCI 38.229000 -86.293999 2.863830 0.028638 0.0271106 2.03282 27.115

WDC 40.580002 -122.540001 12.858200 0.128582 0.121723 9.12708 121.743

WMOK 34.737999 -98.780998 1.342820 0.013428 0.0127119 0.953168 12.714

WUAZ 35.516998 -111.374001 3.457260 0.034573 0.0327283 2.45405 32.7337

WVOR 42.433998 -118.637001 4.970230 0.049702 0.0470509 3.528 47.0587

WVT 36.130001 -87.830002 3.815320 0.038153 0.0361179 2.70821 36.1239

EGMT 47.950001 -109.779999 1.126660 0.011267 0.0106656 0.799733 10.6673

DGMT 48.580002 -104.199997 0.691208 0.006912 0.00654335 0.490638 6.54444

**Sta latitude longitude %g g PGV SG %clip HG %clip**

VKMN 48.220001 -96.410004 0.356017 0.003560 0.00337025 0.25271 3.37081

COWI 46.060001 -89.260002 0.589685 0.005897 0.00558227 0.418573 5.5832

GRMI 44.660000 -84.720001 0.939180 0.009392 0.00889078 0.666654 8.89226

OGNE 41.130001 -101.720001 1.013730 0.010137 0.00959651 0.719572 9.5981

SCIA 42.020000 -93.160004 1.104300 0.011043 0.0104539 0.783861 10.4556

PDNY 44.669998 -74.980003 2.698170 0.026982 0.0255423 1.91523 25.5466

MIME 45.660000 -68.709999 2.144410 0.021444 0.0203001 1.52216 20.3035

MONC 35.200001 -78.070000 1.583770 0.015838 0.0149928 1.1242 14.9953

ATAL 31.020000 -87.489998 1.479430 0.014794 0.0140051 1.05014 14.0074

GHTX 27.170000 -98.120003 0.288432 0.002884 0.00273045 0.204736 2.7309

SNSD 45.060001 -99.510002 0.750744 0.007507 0.00710694 0.532897 7.10812

ANND 47.880001 -100.239998 0.509268 0.005093 0.004821 0.361491 4.8218

AMTX 35.180000 -101.870003 0.955765 0.009558 0.00904778 0.678426 9.04928

BNMN 46.360001 -94.199997 0.442334 0.004423 0.00418737 0.31398 4.18806

BRMT 45.299999 -108.910004 3.247320 0.032473 0.0307409 2.30503 30.746

KCCO 38.759998 -102.790001 1.054920 0.010549 0.00998644 0.74881 9.9881

ERPA 42.130001 -80.089996 1.453010 0.014530 0.013755 1.03138 13.7573

SEKY 36.599998 -83.720001 2.942140 0.029421 0.0278519 2.08841 27.8565

CLKS 37.029999 -97.610001 1.406600 0.014066 0.0133156 0.998441 13.3178

NNNM 36.889999 -109.690002 1.343560 0.013436 0.0127189 0.953694 12.721

MNTX 31.697001 -105.382004 2.613080 0.026131 0.0247368 1.85483 24.7409

**Table 2. Parkfield PGV amplitude convolved with high-gain system
response.**

**Sta latitude longitude distance PGV**

**(km) (m/s)**

MOD 41.9033 -120.305 667 0.00183

HOPS 38.9939 -123.071 421 0.00305

WDC 40.5800 -122.539 558 0.00190

COR 44.5857 -123.303 1003 0.00080

**Appendix 1: Instrument responses**

High-gain STS2 and Q330:

ZEROS 3

0\. 0.

0\. 0.

0\. 0.

POLES 5

-3.70237E-02 3.70244E-02

-3.70237E-02 -3.70244E-02

-251.327 0.

-118.634 423.065

-118.634 -423.065

CONSTANT 4.05950E+17

HOPS:

ZEROS 3

0\. 0.

0\. 0.

0\. 0.

POLES 4

-1.23400E-02 1.23400E-02

-1.23400E-02 -1.23400E-02

-39.1800 49.1200

-39.1800 -49.1200

CONSTANT 3.88355E+12

WDC:

ZEROS 3

0\. 0.

0\. 0.

0\. 0.

POLES 5

-3.70237E-02 3.70244E-02

-3.70237E-02 -3.70244E-02

-251.327 0.

-118.634 423.065

-118.634 -423.065

CONSTANT 2.92868E+16

MOD:

ZEROS 3

0\. 0.

0\. 0.

0\. 0.

POLES 4

-1.23400E-02 1.23400E-02

-1.23400E-02 -1.23400E-02

-19.5900 24.5600

-19.5900 -24.5600

CONSTANT 9.85368E+11

COR:

ZEROS 3

0\. 0.

0\. 0.

0\. 0.

POLES 4

-1.23400E-02 1.23400E-02

-1.23400E-02 -1.23400E-02

-39.1800 49.1200

-39.1800 -49.1200

CONSTANT 4.18246E+12

![](media/image2.png){width="5.990972222222222in"
height="7.753472222222222in"}

**Figure 1**: 10 percent in 30 years 1 Hz spectral acceleration for the
United States.

A)  Assuming Low-gain STS2 instrumentation (red triangles = clipped
    stations).

B)  Assuming high-gain STS2 instrumentation (red triangles = clipped
    stations).

![](media/image3.png){width="5.99375in" height="4.63125in"}

**Figure 2**: Brune source modeled PGV as a function of epicentral
distance. Also plotted is the PGV measured at four stations from the
September 2004 Parkfield M6.0 earthquake.

![](media/image4.png){width="5.990972222222222in"
height="7.753472222222222in"}

**Figure 3**: Seismogram of the Parkfield M6.0 recorded at MOD. Black
line is the original seismogram using an STS1 seismometer. Magenta line
is the waveform convolved with the low-gain recording system. Green line
is the waveform convolved with the high-gain system.

[^1]: USGS ANSS, Golden, CO