Acknowledgements

This project is sponsored by the National Science Foundation EAR/IF program with matching funds from the participating institutions and the Southern California Earthquake Center (SCEC) (PI Romanowicz).

Under Mark Murray's supervision, André Basset, Bill Karavas, John Friday, Dave Rapkin, Doug Neuhauser, Tom McEvilly, Wade Johnson, and Rich Clymer have contributed to the BSL component of the Mini-PBO project. Several USGS colleagues, especially Malcolm Johnston, Bob Mueller, and Doug Myren, played critical roles in the drilling and instrument installation phases.

Figure 8.5: Four-month subset of OHLN strainmeter data, detrended to flatten the first 50 days (middle trace), decomposed using BAYTAP-G into tidal, atmospheric pressure, and "cleaned" data components (with arbitrary vertical offsets). The remaining large strain signals in the cleaned data are highly correlated with rainfall and therefore are likely non-tectonic in origin.

Figure 8.6: Normal modes in the 0.5 to 2.0 mHz band measured on Mini-PBO strainmeters and the BRIB dilatometer following the 2004 M9 Sumatra earthquake. The time window began 8 hours before the event and spans 200 hours. Tides have been removed, but not atmospheric effects, which may account for the higher background noise levels. Figure courtesy of Aimin Cao.