Curie point depth in northeast Japan and its correlation with regional thermal structure and seismicity

Abstract

Heat flow measurements are high on the back arc side and low on the forearc side of the Tohoku arc, but convective heat transfer in volcanic areas affects the heat flow measurements, complicating the determination of the thermal structure from heat flow measurements alone. Curie point depths deduced from previous magnetic analyses show a sudden change of the Curie isotherm between the volcanic front and the Japan Trench. A magnetic belt extends from west Hokkaido to the eastern limit of Tohoku. The location is west of and parallel to the Cretaceous subduction zone. To determine the geometry of the source of the magnetic belt, detailed magnetic analyses were carried out using forward modeling and recently developed spectral analysis techniques. The magnetic analyses indicate that sources of the magnetic belt extend to significant depths. The result reveals that the Curie isotherm varies from 10 km in the back arc to 20 km or deeper at the eastern limit of Tohoku. The boundary between seismic and aseismic zones in the overriding plate correlates with the inferred Curie isotherm, indicating that seismicity in the overriding plate is related to temperature.

Spectral analysis of aeromagnetic data for geothermal energy investigation of Ikogosi Warm Spring - Ekiti State, southwestern Nigeria

“…To quantify the error in the estimated CPD, we evaluated the standard and statistical errors of the power density spectrum from the linear fit using the definition of the error adopted from Trifonova et al (2009) and Okubo and Matsunaga (1994). The results of the spectral analysis of aeromagnetic anomalies over the Ikogosi Warm Spring area show Curie point depth minimum estimates range between 11.5 ± 1.6 and maximum estimates 21.9 ± 1.7 km (Table 1) with an average value of 15.1 ± 0.6 km.…”

“…More recently, investigations have been made for parts of the territory of Japan (by Okubo 1985Okubo , 1989Okubo , 1994, USA (by Mayhew 1985;Blakely 1988), Greece (Tsokas et al 1998;Stampolidis and Tsokas 2002), Portugal (Okubo et al 2003), Bulgaria (Trifonova et al 2006(Trifonova et al , 2009 and Turkey (Dolmaz et al 2005;Maden 2009). Authors consider the power spectrum of the total geomagnetic field intensity anomaly over a single rectangular block using the expression, which was first given by Bhattacharyya (1965).…”

“…Okubo 1994;Tsokas et al 1998;Trifonova et al 2006). Fast Fourier transform (FFT) estimates Fourier components between zero frequency and the Nyquist limit imposed by the grid cell size.…”

Estimating depth to the bottom of magnetic sources at Wikki Warm Spring region, northeastern Nigeria, using fractal distribution of sources approach

“…One of the methods for examining the thermal structure of the crust is the estimation of the CPD using aeromagnetic data (Smith et al, 1977;Okubo et al, 1985Okubo et al, , 1989Okubo et al, , 1994Okubo et al, , 2003Tsokas et al, 1998;Tanaka et al, 1999;Stampolidis and Tsokas, 2002;Dolmaz et al, 2005;Ates et al, 2005;Aydin et al, 2005;Qingqing et al, 2008;Li et al, 2010;Li, 2011;Bilim, 2011;Manea and Manea, 2011;Abd El Nabi, 2012;Hisarli et al, 2012;Saleh et al, 2013;Sayed et al, 2013;Abraham et al, 2014;Obande et al, 2014;Starostenko et al, 2014). Various studies have shown correlations between Curie temperature depths and average crustal temperatures, leading to viable conclusions regarding lithospheric thermal conditions in a number of regions around the world (Ross et al, 2006;Rajaram, 2007;Bouligand et al, 2009).…”

New techniques for estimation of source parameters: Applications to airborne gravity and pseudo-gravity gradient tensors

“…In recent years, this approach is widely adopted for estimating Curie-isotherm depth of the crustal rocks (e.g. Hong et al, 1982;Okubo et al, 1994;Tanaka et al, 1999;Aydin et al, 2005;Ross et al, 2006;Aydin and Oksum, 2010). Abdeslem (1995) introduced a method for interpretation of gravity anomalies using prism model.…”