Onshore-Offshore Data

A major goal of our project is to produce a cross-section of the volcanic arc by recording the Langseth's airgun shots on a dense array of Reftek portable seismometers deployed from coast to coast across Costa Rica. Although we have only looked at a few of records from those instruments, we can already say that the Langseth's airgun shots carried through the arc. Here's the location of a sample record section. The star shows the location of the site, and the red lines show the portion of Line 1E where the shots were fired.

The data (figure below) show clear (though weak) arrivals at source-receiver distances of up to 210 km. The section below shows a "triplication" -- a set of two refractions and a connecting reflection, which in this case come from the middle crust, the crust-mantle boundary (Moho), and the upper mantle. This example is proof-of-concept for using the Langseth for onshore-offshore surveys. We are optimistic that this bodes well for the success of our onshore-offshore program in probing the depths of the volcanic arc.

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