Characterizing the noise for seismic arrays : case of study for the Alice Springs ARray (ASAR)

Abstract

A seismic array is defined as a suite of seismometers with similar characteristics. Seismic array were originally built to detect and identify nuclear explosions. Since their development all over the world, seismic arrays have contributed to study interior of volcanoes, continental crust and lithosphere, determination of core-mantle boundary and the structure of inner core. Seismic arrays have been used to perform many regional tomographic studies (e.g., Achauer and the KRISP Working Group, 1994; Ritter et al., 1998, 2001); they helped to resolve fine-scale structure well below the resolution level of global seismology in many different places in the Earth, from the crust using body waves (e.g., Rothert and Ritter, 2001) and surface waves (e.g., Pavlis and Mahdi, 1996; Cotte et al., 2000), the upper mantle (e.g., Rost and Weber, 2001), the lower mantle (e.g., Castle and Creager, 1999), the core-mantle boundary (e.g., Thomas et al., 1999; Rost and Revenaugh, 2001), and the inner core (e.g., Vidale et al., 2000; Vidale and Earle, 2000; Helffrich et al., 2002). A different branch of seismology that benefited from arrays is “forensic seismology” (Koper et al., 1999; 2001; Koper and Wallace 2003). Studied have been also carried out to track the rapture propagation of large and moderate earthquakes (Goldstein and Archuleta 1991a,b: Spudich and Cranswick 1984; Huang 2001; D’Amico et al. 2010; Sufri et al. 2012; Koper et al. 2012), studies related to the seismic noise have been also developed using seismic arrays (Koper and Fathei, 2007; Gerstoft et al. 2006; D’Amico et al. 2008; Schulte-Pelkum et al., 2004). For example Gerstoft et al. (2006) used beamforming of seismic noise recorded on California Seismic Network to identify body and surface waves generated by the Hurricane Katrina. Schulte-Pelkum et al., (2004) measured direction and amplitude of ocean-generated seismic noise in the western United States. Koper and Fatehi (2007) used 950, randomly chose, 4-sec long time windows from 1996 to 2004 at the CMAR array located in Thailand. In their work they found, around 1Hz, a large noise peak coming from southwest near 220 degrees and an apparent velocity of 3.5-4.0km/s. Their results are robust from year-to-year and are also consistent from season to season. Two lesser noise peaks show probably a seasonal dependence, being much stronger in the fall and winter than in the summer and spring. Neither peak is sensitive to the “hour-to-hour” analysis meaning they are uncorrelated to anthropical noise. Koper and De Foy (2008) showed that the seismic noise recorded at the CMAR array during 1995-2004 can be strongly correlated with the ocean wave’s heights. They carried out this information by using data from TOPEX/POSEIDON satellite tracks and explained them by the local monsoon-driven climate. For all this different purpose a lot of different arrays techniques and methods have been developed (for reviews see: Rost and Thomas, 2002; Filson, 1975) and applied to a wide number of high-quality data set. [excerpt]