2020 NEHRP Provisions Issues
Ground Motion
C. B. Crouse
2016 BSSC Colloquium
Ground-Motion Issues

Multiperiod response spectra

Deterministic caps?

Physics-based models (numerical simulations)

Fault-rupture directivity & 3-D basins

Site coefficients (Fa, Fv, FPGA) for CEUS

Vertical component (Ch. 11.9)

Induced seismicity?

Soil-structure interaction – Ch. 19

Provisions for foundations on piles

Footing-soil modeling & design

Relax some restrictions
New Approach for Computing Long Period Sa
Use Ground Motions from 3-D
Numerical Models to Develop Long
Period Sa Maps
Application: L.A., SEA, SFO, SLC
ASCE 7-22 Standard
Model Regional 3-D Effects on Long Period Motions
a(t)
Basin
Fault
Rock
Southern California Earthquake Center
Utilization of Ground Motion Simulations Committee
(SCEC UGMS)
Goal: develop GM maps for L.A. region

UGMS Committee formed in 2013; meets twice/yr

SCEC performs calculations under UGMS
direction
Los Angeles Sites
LAPD MCER
LAPD (Palmdale) - rock
PSV - cm/sec
100
NGA West2
CyberShake
10
1
10
T - sec
PAS MCER
PAS (Pasadena) - rock
PSV - cm/sec
100
NGA West2
CyberShake
10
1
10
T - sec
COO MCER
Los Angeles Sites
CPP MCER
COO MCER
COO (Compton) - deep basin
PSV - cm/sec
1000
NGA West2
CyberShake
wt average
100
1
10
T - sec
Intermediate Goal of UGMS


MCER maps for L. A. City

Amendment to ASCE 7-16 maps for City

Resource to City and consultants
Look-up tool ~ USGS web app tool