1. CISN Steering and Advisory Committees
When Good Quakes Go Bad Or How Do Small Quakes End Up Being Big And Why Can’t Something Be Done About It?
David Oppenheimer
Presented to
CISN Steering and Advisory Committees
at Caltech, 27 September 2007

2. Where do Noise Events Come from?
Case 1
Bad radio repeater at Oroville causes interference on 7 stations
Automated picks associate into Cape Mendocino “quake”
Coda durations last for s (M5)

3. Where do Noise Events Come from?
Case 2
Small quake occurs at Geysers
Automated “picks” are ok, but Oroville noise adds 2 bad picks.
No codas on BG stations. Oroville again causes codas of s (M5)

4. Chronology of Event #40201796 Time (GMT) (hr:mn:sec) Elapsed (mn:sec)
Action
05:32:46
00:00
Md 5.0 issued V01
05:33:38
00:52
Ml 1.9 update V02
05:35:44
02:58
ShakeMap V01
05:39:09
06:23
Delete message
05:40:05
07:19
ShakeMap V02
05:41:06
08:20
ShakeMap V03
05:41:33
08:47
ShakeMap delete

5. Solutions Make picker smarter RT differentiation of noise from signal
Squash bad magnitudes faster
Stifle ShakeCast generation

6. Making systems smarter

7. Making systems smarter

8. Making systems smarter…
Or, better, eliminate the problem

9. What have we learned? Fine tune criteria for generating ShakeMaps
ShakeCast needs to get smarter
Need to dynamically remove bad stations from system
Clients ascribe (too?) high level of reliability to CISN products.
CISN staff should work with clients to explain limitations