Measurement of seismometer orientation using the tangential P-wave receiver function based on harmonic decomposition

Abstract

S U M M A R YAccurate determination of the seismometer orientation is a prerequisite for seismic studies including, but not limited to seismic anisotropy. While borehole seismometers on land produce seismic waveform data somewhat free of human-induced noise, they might have a drawback of an uncertain orientation. This study calculates a harmonic decomposition of teleseismic receiver functions from the P and PP phases and determines the orientation of a seismometer by minimizing a constant term in a harmonic expansion of tangential receiver functions in backazimuth near and at 0 s. This method normalizes the effect of seismic sources and determines the orientation of a seismometer without having to assume for an isotropic medium. Compared to the method of minimizing the amplitudes of a mean of the tangential receiver functions near and at 0 s, the method yields more accurate orientations in cases where the backazimuthal coverage of earthquake sources (even in the case of ocean bottom seismometers) is uneven and incomplete. We apply this method to data from the Korean seismic network (52 broad-band velocity seismometers, 30 of which are borehole sensors) to estimate the sensor orientation in the period of 2005−2016. We also track temporal changes in the sensor orientation through the change in the polarity and the amplitude of the tangential receiver function. Six borehole stations are confirmed to experience a significant orientation change (10 • −180 • ) over the period of 10 yr. We demonstrate the usefulness of our method by estimating the orientation of ocean bottom sensors, which are known to have high noise level during the relatively short deployment period.

Real-time and in-situ assessment of conduit permeability through diverse long-period tremors beneath Aso volcano, Japan

“…S2). Furthermore, we calibrate the sensor misorientation against longperiod P wave particle-motion, following the approach of Lim et al (2018) and examining the amplitude of tangential receiver functions at zero time. Typically, the estimated sensor misorientation is less than ±3.0°(see also Supplementary material).…”

Orienting and locating ocean-bottom seismometers from ship noise analysis

“…A variety of passive seismological techniques have been developed to orient the horizontal seismometer components, largely based on polarization attributes. Those techniques use a range of seismic observables including surface waves (Laske 1995;Larson 2002;Stachnik et al 2012;Doran & Laske 2017;Scholz et al 2017), body waves (Schulte-Pelkum et al 2001;Fontaine et al 2009;Scholz et al 2017), receiver functions (Janiszewski & Abers 2015;Lim et al 2017) and recordings of ambient noise (Grigoli et al 2012;Zha et al 2013). A crucial downside of passive methods exploiting natural seismic sources is that seismic waves travel through the Earth, which is generally heterogeneous and anisotropic, inducing seismic ray bending and modification of the polarization attributes.…”

Designing and testing a network of passive seismic surveying and monitoring in Dehdasht (South Western Iran)

“…, Lim et al . ). The orientation is usually determined by indirect methods after the installation of the seismometer, and the azimuths of the horizontal components are reported as auxiliary data (e.g., Ekström and Busby ).…”

“…Misorientation of seismometers with respect to the geographic coordinate system is a very important variable for threecomponent seismological analyses that require the rotation of the seismic records from the original geographic coordinates ZNE (vertical, north-south, east-west) into the ZRT (vertical, radial, transverse) or into the ray-oriented LQT (Pwave direction, SV-wave direction, SH-wave direction) coordinate systems. Some examples include earthquake source investigations, anisotropy studies, receiver function analyses or body-and surface-wave polarization studies (e.g., Ekström and Busby 2008;Wilde-Piórko et al 2017, Lim et al 2018). The orientation is usually determined by indirect methods after the installation of the seismometer, and the azimuths of the horizontal components are reported as auxiliary data (e.g., Ekström and Busby 2008).…”