Downloading seismic data (FDSN)

Waveforms and meta data can be retrieved from online FDSN services using the pyrocko.fdsn modules.

Seismic data from Geofon

The following demo explains how to download waveform data and instrument response information. Latter is used to deconvolve the transfer function from the waveform traces in a second step.

from pyrocko.client import fdsn
from pyrocko import util, io, trace

tmin = util.stt('2014-01-01 16:10:00.000')
tmax = util.stt('2014-01-01 16:39:59.000')

# select stations by their NSLC id and wildcards (asterisk)
selection = [
    ('*', 'HMDT', '*', '*', tmin, tmax),    # all available components
    ('GE', 'EIL', '*', '*Z', tmin, tmax),   # all vertical components
]


# Restricted access token
# token = open('token.asc', 'rb').read()
# request_waveform = fdsn.dataselect(site='geofon', selection=selection,
#                                    token=token)

# setup a waveform data request
request_waveform = fdsn.dataselect(site='geofon', selection=selection)

# write the incoming data stream to 'traces.mseed'
with open('traces.mseed', 'wb') as file:
    file.write(request_waveform.read())

# request meta data
request_response = fdsn.station(
    site='geofon', selection=selection, level='response')

# save the response in YAML and StationXML format
request_response.dump(filename='responses_geofon.yaml')
request_response.dump_xml(filename='responses_geofon.xml')

# Loop through retrieved waveforms and request meta information
# for each trace
traces = io.load('traces.mseed')
displacement = []
for tr in traces:
    polezero_response = request_response.get_pyrocko_response(
        nslc=tr.nslc_id,
        timespan=(tr.tmin, tr.tmax),
        fake_input_units='M')
    # *fake_input_units*: required for consistent responses throughout entire
    # data set

    # deconvolve transfer function
    restituted = tr.transfer(
        tfade=2.,
        freqlimits=(0.01, 0.1, 1., 2.),
        transfer_function=polezero_response,
        invert=True)

    displacement.append(restituted)

# Inspect waveforms using Snuffler
trace.snuffle(displacement)

Download fdsn_request_geofon.py

StationXML data manipulation

To manipulate StationXML data through Pyrocko use the pyrocko.fdsn.station module. This example will change the azimuth and dip values for channels whose codes are X, Y and Z, and set all channel instrument’s input units to meters.

from pyrocko.io import stationxml
from pyrocko.example import get_example_data

# Download example StationXML file
get_example_data('responses.xml')

# load the StationXML downloaded data file
sx = stationxml.load_xml(filename='responses.xml')

comp_to_azi_dip = {
    'X': (0., 0.),
    'Y': (90., 0.),
    'Z': (0., -90.),
}

# step through all the networks within the data file
for network in sx.network_list:

    # step through all the stations per networks
    for station in network.station_list:

        # step through all the channels per stations
        for channel in station.channel_list:
            azi, dip = comp_to_azi_dip[channel.code[-1]]

            # change the azimuth and dip of the channel per channel alpha code
            channel.azimuth.value = azi
            channel.dip.value = dip

            # set the instrument input units to 'M'eters
            channel.response.instrument_sensitivity.input_units.name = 'M'

# save as new StationXML file
sx.dump_xml(filename='changed.xml')

Download fdsn_stationxml_modify.py