Tohoku {psd}

Observations of teleseismic strains from the 2011 Tohoku earthquake.

Description

The M_w 9 Tohoku earthquake happened on March 11, 2011. The seismic waves were recorded at stations across the globe, including by borehole strainmeters in the Network of the Americas (NOTA), which was previously known as the Plate Boundary Observatory (PBO) network.

Format

A dataframe with 16000 observations on the following 15 variables.

Dts

The original datetime string, in UTC.

areal

Areal strains

areal.tide

Tidal correction to the areal strains.

areal.baro

Barometric correction to the areal strains.

gamma1

Engineering differential extensional strain: \gamma_1

gamma1.tide

Tidal correction for the \gamma_1 strains.

gamma1.baro

Barometric pressure correction to the \gamma_1 strains.

gamma2

Engineering shear strain: \gamma_2

.

gamma2.tide

Tidal correction for the \gamma_2 strains.

gamma2.baro

Barometric pressure correction to the \gamma_2 strains.

pressure.atm

Atmospheric pressure.

pressure.pore

Pore-fluid pressure.

Dt

The Dts information converted to POSIX datetime.

Origin.secs

The number of seconds relative to the earthquake-origin time.

epoch

Classification based on predicted P-wave arrival: preseismic or seismic.

and 2 attributes:

units

A list of strings regarding the units of various physical quantities given here.

iasp

A list of source and station characteristics, including the the origin time, predicted traveltimes for P and S waves, and the geodetic information used in the traveltime calculation.

Details

These data are for station B084, which is located approximately 8500 km away from the epicenter. Because this distance is large, the seismic waves didn't arrive at this station for more than 700 seconds after the origin time. So there is a record of pre-seismic noise included, the timeseries extends 6784 seconds prior to the origin time, and 9215 seconds after.

The data are classified with the "epoch" variable, which separates the series into pre-seismic and seismic data; this is defined relative to the predicted P-wave arrival time from a traveltime model.

The original dataset contained NA values, which were imputed using zoo::na.locf, which fills NA with the last previous observation.

Source

High frequency strain data archive:

http://borehole.unavco.org/bsm/earthquakes/NeartheEastCoastofHonshuJapan_20110311/

References

USGS summary page:

https://earthquake.usgs.gov/earthquakes/eventpage/official20110311054624120_30/executive

See Also

pspectrum, hfsnm, magnet

TauP.R for an R-implementation of the traveltime calculations

Examples

data(Tohoku)
str(Tohoku)