Technical Studies

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

Boston

The table below provides detailed information on the records generated for Boston 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 Boston 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)
BO01	Simulation, hanging wall	6.5	30	0.39	3000	0.01	29.99	121.97
BO02	Simulation, hanging wall	6.5	30	0.39	3000	0.01	29.99	72.93
BO03	Simulation, foot wall	6.5	30	0.54	3000	0.01	29.99	141.37
BO04	Simulation, foot wall	6.5	30	0.54	3000	0.01	29.99	109.65
BO05	New Hampshire, 1982	4.3	8.4	10.75	3847	0.005	19.23	564.78
BO06	New Hampshire, 1982	4.3	8.4	10.75	3847	0.005	19.23	309.51
BO07	Nahanni, 1985	6.9	9.6	0.09	4068	0.005	20.335	86.29
BO08	Nahanni, 1985	6.9	9.6	0.09	4068	0.005	20.335	81.18
BO09	Nahanni, 1985	6.9	6.1	0.2	3752	0.005	18.755	59.48
BO10	Nahanni, 1985	6.9	6.1	0.2	3752	0.005	18.755	72.23
BO11	Nahanni, 1985	6.9	18	0.92	3804	0.005	19.015	130.69
BO12	Nahanni, 1985	6.9	18	0.92	3804	0.005	19.015	133.21
BO13	Saguenay, 1988	5.9	96	1.57	3548	0.005	17.735	196.50
BO14	Saguenay, 1988	5.9	96	1.57	3548	0.005	17.735	284.44
BO15	Saguenay, 1988	5.9	98	3.21	2958	0.01	29.57	513.58
BO16	Saguenay, 1988	5.9	98	3.21	2958	0.01	29.57	243.68
BO17	Saguenay, 1988	5.9	118	3.25	3906	0.01	39.05	179.47
BO18	Saguenay, 1988	5.9	118	3.25	3906	0.01	39.05	222.98
BO19	Saguenay, 1988	5.9	132	3.34	3325	0.01	33.24	172.96
BO20	Saguenay, 1988	5.9	132	3.34	3325	0.01	33.24	267.23

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