Comment on "Fractal analysis of ULF electromagnetic emissions in possible association with earthquakes in China" by Ida et al. (2012)

Abstract. Ida et al. (2012) identified anomalous decreases in the fractal dimension of the vertical (Z) component of the geomagnetic field, which they interpreted as precursors to the China earthquake of 1 September 2003. According to Ida et al. (2012), short-term earthquake prediction seems to be possible only by using electromagnetic phenomena. Here, it is shown that the decreases of the fractal dimension documented by Ida et al. (2012) are not really anomalous, but they are part of the normal geomagnetic activity driven by solar–terrestrial interactions. As a consequence, these fractal dimension decreases are not related to the 1 September 2003 earthquake.