Technical Studies

Earthquake Ground Motions with 10% Probability of Exceedence in 50 Years

Seattle

The table below provides detailed information on the records generated for Seattle having probabilities of exceedence of 10% in 50 years. These acceleration time histories have been derived from historical recordings or from physical simulations and have been altered so that their mean response spectrum matches the 1997 NEHRP design spectrum, modified from soil type of S_B-S_C to soil type S_D and having a hazard specified by the 1997 USGS maps.

There are 20 different horizontal components (10 2-component records). Each original historical ground motion pair has typically been altered in the following way:

The two horizontal components originally provided were resolved into fault-normal and fault-parallel orientations.
The records are adjusted in the frequency domain to have characteristics appropriate for NEHRP S_O soil sites.
The records are amplitude scaled so that the average of the two horizontal spectra match the target spectrum.
The individual components were rotated 45 degrees away from the fault-normal fault-parallel orientations

Additional details can be found from the main Ground Motions page. This page also provides a link to a draft report summarizing all of the SAC Phase 2 ground motion studies.

To see the acceleration time history of any of the ground motions listed in the table below, just click on the ground motion name.

Details of Seattle Ground Motions Having a
Probability of Exceedence of 10% in 50 Years
SAC Name	Record	Earthquake Magnitude	Distance (km)	Scale Factor	Number of Points	DT (sec)	Duration (sec)	PGA (cm/sec²)
SE01	Long Beach, Vernon CMD Bldg.	6.5	1.2	0.49	3909	0.01	39.08	170.55
SE02	Long Beach, Vernon CMD Bldg.	6.5	1.2	0.49	3909	0.01	39.08	132.70
SE03	Morgan Hill, 1984, Gilroy	6.2	15	2.84	3000	0.02	59.98	378.82
SE04	Morgan Hill, 1984, Gilroy	6.2	15	2.84	3000	0.02	59.98	649.80
SE05	West. Washington, Olympia, 1949	6.5	56	1.86	4000	0.02	79.98	376.18
SE06	West. Washington, Olympia, 1949	6.5	56	1.86	4000	0.02	79.98	345.11
SE07	West. Washington, Seattle Army B., 1949	6.5	80	5.34	3335	0.02	66.68	289.19
SE08	West. Washington, Seattle Army B., 1949	6.5	80	5.34	3335	0.02	66.68	381.26
SE09	North Palm Springs, 1986	6	6.7	1.71	3000	0.02	59.98	576.45
SE10	North Palm Springs, 1986	6	6.7	1.71	3000	0.02	59.98	558.10
SE11	Puget Sound, Wa., Olympia, 1949	7.1	80	4.3	4092	0.02	81.82	737.82
SE12	Puget Sound, Wa., Olympia, 1949	7.1	80	4.3	4092	0.02	81.82	584.52
SE13	Puget Sound, Wa., Federal OFC B., 1949	7.1	61	5.28	3705	0.02	74.08	362.31
SE14	Puget Sound, Wa., Federal OFC B., 1949	7.1	61	5.28	3705	0.02	74.08	297.30
SE15	Eastern Wa., Tacoma County, 1949	7.1	60	8.68	3000	0.02	59.98	284.72
SE16	Eastern Wa., Tacoma County, 1949	7.1	60	8.68	3000	0.02	59.98	563.47
SE17	Llolleo, Chile 1985	8	42	1.24	4000	0.025	99.975	684.27
SE18	Llolleo, Chile 1985	8	42	1.24	4000	0.025	99.975	657.89
SE19	Vinadel Mar, Chile, 1985	8	42	1.69	4000	0.025	99.975	531.05
SE20	Vinadel Mar, Chile, 1985	8	42	1.69	4000	0.025	99.975	376.88

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