Advanced Exercise Solution 4b

from __future__ import print_function

from math import log10

import numpy as np

from obspy.clients.arclink import Client
from obspy import UTCDateTime
from obspy.geodetics import gps2dist_azimuth


paz_wa = {'sensitivity': 2800, 'zeros': [0j], 'gain': 1,
          'poles': [-6.2832 - 4.7124j, -6.2832 + 4.7124j]}

client = Client(user="sed-workshop@obspy.org")
t = UTCDateTime("2012-04-03T02:45:03")

stations = ["LKBD", "SIMPL", "DIX"]
mags = []

for station in stations:
    st = client.get_waveforms("CH", station, "", "[EH]H*", t - 300, t + 300,
                              metadata=True)

    st.simulate(paz_remove="self", paz_simulate=paz_wa, water_level=10)
    st.trim(t, t + 50)

    tr_n = st.select(component="N")[0]
    ampl_n = max(abs(tr_n.data))
    tr_e = st.select(component="E")[0]
    ampl_e = max(abs(tr_e.data))
    ampl = max(ampl_n, ampl_e)

    sta_lat = st[0].stats.coordinates.latitude
    sta_lon = st[0].stats.coordinates.longitude
    event_lat = 46.218
    event_lon = 7.706

    epi_dist, az, baz = gps2dist_azimuth(event_lat, event_lon, sta_lat,
                                         sta_lon)
    epi_dist = epi_dist / 1000

    a = 0.018
    b = 2.17
    ml = log10(ampl * 1000) + a * epi_dist + b
    print(station, ml)
    mags.append(ml)

net_mag = np.median(mags)
print("Network magnitude:", net_mag)