1. Ken Hudnut U.S. Geological Survey hudnut@usgs.gov 22 November 2013
Real-time GPS PPP(AR) Assists Earthquake Early Warning; Field Deployment USGS “Virtual” Geodesy Meeting
Overview of real-time GPS for use in earthquake early warning.
Ken Hudnut
U.S. Geological Survey
22 November 2013

2. Long Term Vision
Install near-field instrumentation to rapidly detect displacements along major faults like the San Andreas – implement the “Zipper Array” concept
Improve GPS real-time technology; accuracy, precision, timeliness, robustness, reliability
Test, procure, and deploy gear on an ongoing basis
Develop new ways to use low-latency displacement data in EEW algorithms; Slip Sensor & Regional
As a byproduct, obtain data in a future great earthquake that could potentially revolutionize our understanding of earthquake source physics

3. Lone Juniper Ranch and Frazier Park High School
Prototype GPS fault slip sensor
Spans the San Andreas fault near Gorman, California
Need robust GPS at all key lifeline crossings
Desirable to include seismic with GPS
Hudnut et al., 2002

4. Proposed a zipper array for early warning and immediate finite-fault source for San Andreas and San Jacinto fault ‘Big Ones’
Los
Angeles
2007
IOC - 36 quadrilaterals 30 km spacing (shown)
FOC km spacing ($5 M init. + $1 M/yr)

5. San Andreas fault
2013

6. Observing Static & Dynamic Displacements
In near-field region, Ddynamic > Dstatic
- very useful for EEW algorithms
- e.g., Yamada, Heaton, Aagaard
- FinDer (Böse, Heaton & Hauksson, 2012)
Fault slip means displacements are instantaneous
right at the fault, move with rupture front
Direct observation of displacement is fastest
Displacements decrease with 1/r2
At distances > 50 km, surface wave amplit.’s
will exceed displacements and static will
travel out at approx. S-wave velocity
Examine rapid post-seismic behavior (friction law?)
Dstatic
Ddynamic

7. (Böse, Heaton, Hudnut, Felizardo et al.)
CISN ShakeAlert
Courtesy of M. Böse
Fault Slip Detector (‘GPSlip’)
(Böse, Heaton, Hudnut, Felizardo et al.)
Idea:
Back-projection of dynamic displacement
(at GPS sensor) onto fault to estimate slip
Yamada, Heaton, Aagaard
Example:
Application to waveform simulations of M7.8 ShakeOut Scenario by Graves et al., 2008
observed surface slip
estimated slip
along San Andreas Fault

8. Fault Slip Detector (‘GPSlip’)
CISN ShakeAlert
Courtesy of M. Böse
Fault Slip Detector (‘GPSlip’)
(Böse, Heaton, Hudnut, Felizardo et al.)
slip legend
GPS sensors and estimated slip
Slip estimated from back-projection using ShakeOut waveform simulations by Graves et al., 2008

9. Fault Slip Detector (‘GPSlip’)
CISN ShakeAlert
Courtesy of M. Böse
Fault Slip Detector (‘GPSlip’)
Current Processing:
(Böse, Heaton, Hudnut, Felizardo et al.)
USGS Pasadena
Caltech
GPS sensor
Real-time estimation of fault slip
(using back-projection)
raw data
RTK/PPP(AR) using RTNet software
position
time series
for each sensor location
(JSON format)
UserDisplay
GPS sensor
internal testing
GPS sensor .
Status:
no 24/7 operation
need to create associator, hardening software
need to connect to other ShakeAlert algs, in particular FinDer

10. Fault Slip Detector (‘GPSlip’)
CISN ShakeAlert
Courtesy of M. Böse
Fault Slip Detector (‘GPSlip’)
Future Processing:
(Böse, Heaton, Hudnut, Felizardo et al.)
USGS Pasadena
Caltech
GPS sensor
Real-time estimation of fault slip
(using back-projection)
raw data
RTK/PPP(AR) using RTNet software
position
time series
for each sensor location
(JSON format)
UserDisplay
GPS sensor
internal testing
TOPCON and other receivers
GPS sensor
...
Real-time conversion to EW tracebuf2
GPS sensor
GSOF
~40 sites
NetR9 with RTX
...

11. Real-time output from GPS receiver… “paradigm shift” “revolutionary”
-0.203
-0.204
-0.201
-0.189
-0.184
-0.1
-0.138
-0.104
0.0004
-0.145
-2.198
12.767
12.744
1.072
1.104
2.922
-64.77
Displacement
test results
simulating 150 cm
dynamic and 75 cm
static earthquake
repeated offsets
… special purchase
by Caltech with new
UASI funds for EEW
from City of LA
10 Hz output to EEW
- position
- velocity
Deploy to ‘zipper’ array
as upgrades under way
Real-time
output from
GPS receiver…
“paradigm shift”
“revolutionary”

12. Field deployment half-way completed: NetR9 RTX field performance at
~10 mm RMS horiz.
~20 mm RMS vert.
is even better than
expected (due to
GLONASS & revised
receiver configuration
settings)

13. Senator Padilla and
Doug Given, USGS
Governor Signs California Earthquake Early Warning Bill
Governor Jerry Brown signed the California earthquake early warning bill, SB 135, on September 24, The bill calls for Cal OES in collaboration with USGS, CISN, State agencies and private partners to “develop a comprehensive statewide earthquake early warning system in California.”  Cal OES has until January of 2016 to identify funding for the system “through single or multiple sources of revenue that shall be limited to federal funds, funds from revenue bonds, local funds, and private grants.”  State General Funds are specifically excluded as a source. 

14. USGS “zipper array” along San Andreas for early warning
Ken Hudnut
(626)
USGS “zipper array” along San Andreas for early warning