Map 8-1   Purcell Trench

Map 8-2

identifier
Quaternary Fault and Fold Database for the United States

 

Idaho

Idaho

Last modified November 17, 2004  

URL http://geohazards.cr.usgs.gov/qfaults/id/index.html

The National Seismic Hazard Mapping Project produces maps showing national earthquake hazards expressed as probabilistic ground motions. The probabilistic ground motion value for any desired site in the United States can be looked up by latitude and longitude, or by zip code at http://eqint.cr.usgs.gov/eq/html/lookup-2002-interp.html or at the Earthquake Hazards Program website http://eqhazmaps.usgs.gov/faq/psha02.html (as seen in Table 8-1, below).  This site also provides definitions of Peak Ground Acceleration (PGA) and 0.2 and 1.0 sec Spectral Acceleration (SA).  

Table 8-1.  Probabilistic Ground Motions for Bonners Ferry

USGS, Earthquake Hazards Program - National Seismic Hazard Mapping (Link to USGS home page.) 

   The input zip-code is 83805.  Bonners Ferry, Idaho


   ZIP CODE                        83805


   LOCATION                        48.6977 Lat. -116.3169 Long.


   DISTANCE TO NEAREST GRID POINT  1.2672 kms


   NEAREST GRID POINT              48.7 Lat. -116.3 Long.


   Probabilistic ground motion values, in %g, at the Nearest Grid point are:


               10%PE in 50 yr   5%PE in 50 yr   2%PE in 50 yr


      PGA        6.330679         8.697392       13.437380


   0.2 sec SA   13.833410        18.982620       30.260580


   0.3 sec SA   12.398080        17.682159       27.169500


   1.0 sec SA    4.224729         6.044158        9.142096


   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Map 8-3

Probability of Exceedance for Boundary County

See http://eqhazmaps.usgs.gov/faq/parm03.html for a definition of Probability of Exceedance (PE).  PE values are given for firm rock and may change over short distances because of local soil conditions.

 

 

  



Map 8-4





  

  

    

      
    

  

  




This seismic hazard map for Idaho shows earthquake ground motions
that have a specified probability of being exceeded in 50 years. These ground
motion values are used for reference in construction design for earthquake
resistance. The ground motion values can also be used to assess relative hazard
between sites, when making economic and safety decisions (http://eqhazmaps.usgs.gov/
accessed 1/18/05).


LEPC Relative Risk Rating 
The LEPC gave earthquake was given a relative risk hazard rating of
“8.”  The LEPC determined that
over 75 percent of the developed area of the county would be impacted should an
earthquake occur.  Although the
probability of earthquake occurrence is unknown, the LEPC consensus, based on
available information, is that it would be rare to have an earthquake that would
have substantial negative impact to property, environment, health and safety of
people, or the economy in Boundary County. 
Map 8-5 below shows the risk of earthquake in Boundary County to be
moderate.




 




 




Map
8-5    Earthquake Risk for
Idaho




 





  

  

    

      
    

  

  




Map
8-6




 





  

  

    

      
        
Seismicity of Idaho, 1990 - 2001

    

    

      
    

    

      
    

  

  









 




Map
8-7   Locations of Earthquakes
in Boundary County




As Documented by Idaho
Bureau of Homeland Security






 





  

  

    

      
    

    

      Three significant earthquakes have been documented by the Idaho Bureau
        of Homeland Security since 1952.   No
        damage was recorded for any of these events.  On
        September 9, 1952, a 4.0 magnitude earthquake occurred near the City of
        Bonners Ferry.  On July 30,
        1984 there was a 4.1 magnitude north of the city of Moyie Springs. 
         On November 27, 1984,  a
        3.2 magnitude quake occurred approximately ten miles to the north of
        Bonners Ferry.
    

  

  





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