AgdaPkt 2018-05-21 Joint SA PFA - Laserfiche WebLink

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353 Main Street Apartments Redwood City, California May 1, 2018 (Original Report Doted November L8,20L6) classified faults based on the rate of their seismicity and likelihood of generating damaging earthquakes. Type A sources were defined as faults that have sufficient data on the location, timing, and slip in previous earthquakes that permanent rupture boundaries can be hypothesized. Type B sources were defined as faults that have slip-rate estimates but where data on distribution and timing of previous events are inadequate to estimate recurrence intervals. Type C sources were defined as crustal shear zones where significant strain is accumulated but where knowledge is insufficient to apportion slip onto specific faults. Type A faults have generally produced the strongest earthquakes, but Type B faults are capable of producing earthquakes of significa nt magnitude. The closest Type A fault is the San Andreas located approximately 4.3 miles to the west. The closest Type B fault is the Monte Vista - Shannon fault located approximately 3.7 miles southwest of the site. 3.0 FIELD INVESTIGATION AND LABORATORY TESTING Subsurface Exploration The subsurface soil conditions at the site were explored by drilling four borings to depths ranging from 20 to 50 feet bgs and advancing four Cone Penetration Tests (CPT) to depths ranging from 60 to 70 feet below ground surface. The Site Plan, Figure 2, shows the approximate locations of the test borings and CPT soundings. Copies of the boring logs and CPT soundings are presented in Appendix A. Drilled Test Borinss The exploratory borings were drilled under the direction of an Earth Systems engineer Subsurface conditions encountered in the borings were described to create a continuous profile of soil profile at the drilling location (boring log). The logs of soil borings include soil description in general accordance with the Unified Soil Classification System (ASTM D 2488-L71, penetration resistance data, sampling intervals, sample collection method, and the changes in soil conditions with depth. The penetration resistance data was used to estimate consistency of cohesive soils and relative density of granular soils. Soil samples were obtained from the borings at 3- to S-foot depth intervals or where changes in the soiltypes were observed. The samplers were driven into undisturbed soil using a L40-pound hammer with a 3O-inch fall. Penetration resistance was recorded as the number of hammer blows required to drive the last foot of samplers into undisturbed ground. Relatively undisturbed samples were collected using Modified California sampler internally-lined with 6-inch long brass tubes. Standard Penetration Test samplers were used generally in granular soils and the 3301842-001 r.610-038.SER.REV2 7.B. - Page 61