Set default seismogram output as ascii.

[icui]

Description

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Issue Number

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Checklist

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[x] I ran the code through pre-commit to check style [x] My code passes all the integration tests [x] I have added sufficient unittests to test my changes [x] I have added/updated documentation for the changes I am proposing [x] I have updated CMakeLists to ensure my code builds [x] My code builds across all platforms

[buildbot-princeton]

Can one of the admins verify this patch?

[buildbot-princeton]

Can one of the admins verify this patch?

[Rohit-Kakodkar]

ok to test