Beginner: plotting focal mechanism

Q&A GMT.jl Q&A
1

Dear gmt users,

I would like to map multiple focal mechanisms with gmt.
When I use just the example in the site, I can draw a focal mechanism with additional codes:

gmt begin focal png

gmt psmeca -R239/240/34/35.2 -Jm4c -Sc0.4 -h1 << END > test.ps
lon lat depth str dip slip st dip slip mant exp plon plat
239.384 34.556 12. 180 18 -88 0 72 -90 5.5 0 0 0
END

gmt end show

But,

I have a couple of questions In this example.

1.Why do I have to type dip and slip twice (72 and -90) in the example?
If I do not know the second dip and slip, how do I make the focal mechanism?
When I just put zeros in the second dip and slip, it shows different figure.

2.What do these slip, st, exp, plon, and plat mean in the example?
The Slip means Rake?
I know the ''Rake" of each earthquake. Where do I have to enter?
Could you give me some references?

Thank you for reading this post

2

Think you need to read the -S documentation and select the data format you have. If your data is not in any of the five standard formats then you will need to do some reformatting yourself.

3

Yes, you’re right. I will try more. Thank you for your reply.