In this directory, there are preliminary GPS results for September 5, 2012
M7.6 Costa Rica earthquake provided by the ARIA team at JPL and Caltech. These
files are coseismic and postseismic offsets and kinematic precise point
positioning solutions using JPL's GIPSY-OASIS software, including single
station bias fixing method, and JPL's orbit and clock products.

In your use of these time series, please use the following accreditation:

"Preliminary GPS time series provided by the ARIA team at JPL and Caltech.
All original RINEX data provided to JPL by UNAVCO."

For more information on the network and the tectonics of the region, please
see the "Nicoya-Dixon.pdf"file included in this directory by
Professor Tim Dixon of University of South Florida. 

Offsets - Explanation of Naming Convention
--------------------------------------------

The name of the file gives the position estimate interval (e.g.,
"Daily" or "5min"), the lowest fidelity orbits used for the
solution (e.g., "UltraRapid", "Rapid", "Final"), the
type of offset (e.g., "coseismic" or "postseismic"). For
"postseismic", the date gives the most recent day included in the
postseismic offset calculation.

Coseismic Offset - Daily" Method
--------------------------------
The pre-earthquake position is estimated using a linear velocity fit to 38
days prior to event for all sites except for HUA2. HUA2 has pre-earthquake
data up to 204 (July 22), so the HUA2 pre-event position is based on linear
velocity fit to two months of data from May 26 to July 22, 2012.  

The post earthquake position is a single daily position estimate from day 250
(Sept 6) except for HUA2 - that is from day 251 (Sept 7).   

As of Sept 11, 2012, daily positions estimated for days after Sept 1, 2012 use
JPL's Rapid orbits and clocks -- prior to Sept 1, 2012, positions are
estimated with Final orbits and clocks. 

Postseismic Offset - "Daily" Method
--------------------------------
Postseismic offsets are a difference between daily positions for date tiven in
the file name and day 250 (Sept 6) for all sites except for HUA2 where first
post-eq data is from day 251 (Sept 7).

PDF plot of offsets
-------------------
In the plot "Daily.Rapid_co_and_postseismic_offsets.20120911.pdf", coseismic
and postseismic vectors are plotted at different scales for comparison of the
spatial pattern. Black vectors show coseismic horizontal displacemets and blue vectors
represent coseismic vertical displacements. Red (horizontal) and green
(vertical) represent postseismic offsets up to Sept 10, 2012. 

Time Series Subdirectories
--------------------------
In subdirectories, we have posted time series for the day of the earthquake
using different kinematic positioning analysis strategies and products.
Naming Convention

The name of the subdirectory gives the orbit type used (e.g., "UltraRapid",
"Rapid", or "Final") and, if there are multiple solutions for
one orbit type, the solution interval (e.g., "5hz", "30 sec",
or "5min")

Explanation of llh_cal files
------------------------

Each file contains set of 3 rows for each solution epoch. They are same
solution, in different formats

1st row - lat, lon, height (m), sigma (m)
2nd row ("nev") - north, east, up, sigma in meters (relative to first epoch
solution)
3rd row ("est") - north, east, up, sigma in meters (relative to a priori
position value)

Columns are:

Year Month Day Hour Min Sec "J2000 seconds"  obs1 obs2 obs3 Sigma Site "row
name"

Time tags are in GPS Time (offset from UTC since GPS time is not perturbed by
leap seconds, which meant GPS time was 16 seconds ahead of UTC time at time of
Costa Rica earthquake).