DataAnalysis2022/ObsPy/07_Basic_Processing_Exercise.ipynb

ObsPy Tutorial

Downloading/Processing Exercise

Seismo-Live: http://seismo-live.org

Authors:

• Lion Krischer (@krischer)
• Tobias Megies (@megies)

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For the this exercise we will download some data from the Tohoku-Oki earthquake, cut out a certain time window around the first arrival and remove the instrument response from the data.

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%matplotlib inline
import matplotlib.pyplot as plt
plt.style.use('ggplot')
plt.rcParams['figure.figsize'] = 12, 8

The first step is to download all the necessary information using the ObsPy FDSN client. Learn to read the documentation!

We need the following things:

1. Event information about the Tohoku-Oki earthquake. Use the get_events() method of the client. A good provider of event data is the USGS.
2. Waveform information for a certain station. Choose your favorite one! If you have no preference, use II.BFO which is available for example from IRIS. Use the get_waveforms() method.
3. Download the associated station/instrument information with the get_stations() method.

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Have a look at the just downloaded data.

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Exercise

The goal of this exercise is to cut the data from 1 minute before the first arrival to 5 minutes after it, and then remove the instrument response.

Step 1: Determine Coordinates of Station

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Step 2: Determine Coordinates of Event

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Step 3: Calculate distance of event and station.

Use obspy.geodetics.locations2degree.

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Step 4: Calculate Theoretical Arrivals

from obspy.taup import TauPyModel
m = TauPyModel(model="ak135")
arrivals = m.get_ray_paths(...)
arrivals.plot()

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Step 5: Calculate absolute time of the first arrivals at the station

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Step 6: Cut to 1 minute before and 5 minutes after the first arrival

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Step 7: Remove the instrument response

st.remove_response(inventory=inv, pre_filt=...)

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Bonus: Interactive IPython widgets

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from IPython.html.widgets import interact
from obspy.taup import TauPyModel

m = TauPyModel("ak135")

def plot_raypaths(distance, depth, wavetype):
    try:
        plt.close()
    except:
        pass
    if wavetype == "ttall":
        phases = ["ttall"]
    elif wavetype == "diff":
        phases = ["Pdiff", "pPdiff"]
    m.get_ray_paths(distance_in_degree=distance,
                    source_depth_in_km=depth,
                    phase_list=phases).plot();
    
interact(plot_raypaths, distance=[0, 180],
         depth=[0, 700], wavetype=["ttall", "diff"]);