Plot FocalMechanims

Q&A PyGMT Q&A
1

Dear all,
I was trying to plot focal mechanism solutions based on aki format, however I got the following error:

GMTInvalidInput: Arguments in short-form (C) and long-form (offset) can't coexist

My input file is attached gCMT_sols.dat (762 Bytes)

The code I am using to plot the focal mechanism is:

df_focal_mecha = pd.read_csv('gCMT_sols.dat', sep='\s+')

df_focal_mecha.head()

fig.meca(
    spec=df_focal_mecha,
    convention = 'aki',
    scale="1.0c",
    C=True,
    offset = True,
    )

Dis I do a mistake over the input format?
Thanks in advance
Tonino

2

First of all you need to define a cpt before using C = True:

import pygmt

fig = pygmt.Figure()
pygmt.makecpt(cmap= "roma")

fig.meca(
    spec = 'gCMT_sols.dat',
    convention = 'aki',
    scale = "1.0c",
    offset = True,
    frame = True,
    C = True)  

fig.show()

which gives you the following:

index
index1833Ă—1855 52.4 KB

However, I assume you want to color your focal mechanisms based on depth or something like that?

3

Dear @mgrund,
Thank you for the answer. Yes I’d like to color according to depth. Should I create a color map too rigth?
Tonino

4

In principle, yes. Depending on how your input data is formatted, depth should be in the third column. However, your data has 9 columns and the filename contains “gCMT”, on the other side you set convention to 'aki'. Is your data in the right format?

5

@mgrund, about the input file, the data comes from GCMT for that reason I named gCMT.
The input is “sorted” like the AKI format, however the last two columns are offset where I’d like to plot the beach-balls (same as GMT input), however I am not able to plot with offset the beach-balls.

6

@mgrund, I just updated the version of PyGMT to newest and it’s running smooth the offset for beach-balls, thank you, stay safe and best regards
Tonino

7

Dear @mgrund,
It worked, here I paste the code, just in case anyone need it.

pygmt.makecpt(cmap = 'hot',
                  series = [1,70,3])  

fig.meca(
    spec='Nieto_sols.dat',
    convention = 'aki',
    scale="0.7c",
    offset = True,
    frame = True,
    C = True
    )           

fig.colorbar(frame=["x+lFM-Depth", "y+lkm"], position="JMR+o0.5c/0c+w8c")

Stay safe and best regards,
Tonino

Map-Nieto-Focal-Mechanism
Map-Nieto-Focal-Mechanism1901Ă—1232 74.7 KB

8

Dear @tonino13,

Thank you very much for posting your code for coloring focal mechanisms by depth. I hadn’t updated PyGMT to v0.5.0 but have now done that and this seems to have been the final step required to crack the problem. Like you, I think, I also found I had to write my data frame out as a tab-separated file and then read it in again, instead of passing it directly to meca.

Thanks again and best wishes from Wellington,
John T.

9

The GMT must be installed to work with pygmt

10

i cant still plotting offset for beachballs???
data input coulmn is lon lat depth strike dip slip mag plot_lon plot_lat with txt format
whats problem
and i installed last version pygmt 7.0

11

Hi @kami, your input data file must have the following format:

Lon Lat Depth Strike Dip Rake Mag OffsetLon OffsetLat

For exmaple, in a txt file you should have:

-65.700 -17.108 4.6 114.78 39.78 45.35 4.4 -65.516 -17.148

The last two columns (OffsetLon and OffsetLat) are the place where you want to plot the Focal Mechanism.

I hope this help, stay safe,
Tonino

12

Dear @tonino13 thanks for reply. see my input file What do you think?

Screenshot from 2022-04-12 02-29-02
Screenshot from 2022-04-12 02-29-021094Ă—391 60.6 KB

13

I think, input file reads all the columns in just one column

14

my code with its error is:

​data=pd.read_csv(“focmec.txt”)
lon lat depth strike dip rake mag p_lon p_lat
0 53.48 36.07 12.2 220.7 52.3 170.4 4.6 53.1 36.2
1 55.09 36.98 16.1 316.6 64.7 -190.1 5.2 55.1 37.2
2 53.01 36.67 25.1 137.6 28.5 91.0 4.7 54.2 35.9

fig.meca(spec=data, convention=“aki”, scale=“0.7c”,plot_longitude=True, plot_latitude=True, offset=True)
raise GMTError(
pygmt.exceptions.GMTError: Parameters in spec dictionary do not match known conventions.

15

if the leading 0, 1, 2 is in your data file then you are off by one column - you gotta get rid of those running numbers.

16

Dear @pwessel your comment is true. i change input data to this

data=pd.read_csv(“focmec.csv”, header=None,delimiter=“\s+”)

data
0 1 2 3 4 5 6 7 8
0 53.48 36.07 12.2 220.7 52.3 170.4 4.6 53.1 36.2
1 55.09 36.98 16.1 316.6 64.7 -190.1 5.2 55.1 37.2
2 53.01 36.67 25.1 137.6 28.5 91.0 4.7 54.2 35.9
but it doesnt still work.
If possible you give me a csv file that you with it plotted offset and i will try with it.

17

Sorry, I do not use pyGMT so I do not know if the read_csv command inserts those running numbers 0 1 2 etc or if they are in your data file. Maybe @seisman can suggest something?

18

@kami, can you reply with the first few lines from focmec.csv so that we can see what the raw data look like?