The study of ionospheric anomalies in Japan area during 1998–2010 by Kon et al.: An inaccurate claim of earthquake-related signatures?

The problem of identifying precursory signals of earthquakes in the hope of mitigate the seismic hazard is a very important topic, but inaccurate documentations of precursory signatures decrease the credibility of this field of research. The statistical analysis by Kon et al. (2011) shows that there is tendency of positive total electron content (TEC) anomalies to occur 1–5 days before 52 M > 6 earthquakes which struck Japan during 1998–2010. Kon et al. (2011) also report in detail three selected case studies claiming the occurrence of TEC anomalies possibly related to large and destructive earthquakes. This paper casts doubts on the possibility that in the three cases the TEC disturbances were caused by seismic events suggesting that these TEC changes could be induced by normal variations of the global geomagnetic activity. As a consequence, also the results of the Superimposed Epoch Analysis performed by Kon et al. (2011) could be seriously influenced by global magnetospheric signals

Comment on ‘‘Possible association between anomalous geomagnetic variations and the Molise Earthquakes at Central Italy during 2002’’ by Takla et al. (2011)

Takla et al. (2011) documented the observation of seismogenic precursory signals in the geomagnetic field components of L’Aquila station (LAQ) which occurred before the 2002 Molise earthquakes. Here, these claims are reviewed taking into account the geomagnetic index ΣKp time-series and by means of data coming from the Geomagnetic Observatory of L’Aquila where the LAQ station is located. This review shows that before the Molise earthquakes the anomalous behaviour of LAQ geomagnetic field components was actually caused by a possible thermal drift of the instrumentation. In conclusion there is no firm relation between the earthquakes occurrence and the observed magnetic anomalous signatures documented by Takla et al. (2011)

Comment on “Ultra Low Frequency (ULF) European multi station magnetic field analysis before and during the 2009 earthquake at L’Aquila regarding regional geotechnical information” by Prattes et al. (2011)

Prattes et al. (2011) report ULF magnetic anomalous signals claiming them to be possibly precursor of the 6 April 2009 MW6.3 L’Aquila earthquake. This comment casts doubts on the possibility that the observed magnetic signatures could have a seismogenic origin by showing that these pre-earthquake signals are actually part of normal global geomagnetic activity

On the multi-fractal characteristics of the ULF geomagnetic field before the 1993 Guam earthquake

Ida et al. (2005) document significant changes in the multi-fractal parameters of the ULF geomagnetic field H component starting about one month before the 1993 Guam earthquake. According to the authors, these multi-fractal signatures can be considered as precursory signals of the Guam earthquake. As a consequence, they conclude that the multifractal analysis may have an important role in the development of short-term earthquake prediction capabilities. Since this and other similar reports have motivated the idea that earthquake prediction based on electromagnetic precursory signals may one day become a routine technique, the presumed precursors need to be validated through independent datasets. In this review the seismogenic origin of the multifractal magnetic signatures documented by Ida et al. (2005) before the 8 August 1993 Guam earthquake is seriously put into question. By means of the geomagnetic ΣKp index, it is demonstrated that these multi-fractal parameter changes are normal signals induced by the variation of the global geomagnetic activity level

ON THE PRESUMED ULF MAGNETIC PRECURSORS OF EARTHQUAKES

During the last twenty years many researchers investigated ULF (Ultra-Low- Frequency) magnetic data in the hope of finding seismogenic signals. After the report of Fraser- Smith et al. (1990) several ULF stations were installed and many papers documented the observations of pre-earthquake magnetic anomalies. These claims motivate the belief that one day short-term earthquake prediction based on magnetic data may become a routine technique. Shortterm earthquake prediction has been the topic of several scientific debates but at present the entire subject remains still controversial. In order to be useful, short-term prediction requires reproducible earthquake precursors which provide information regarding intensity, location and time of the predicted earthquake together with error estimates for each parameter. Thus, a serious problem concerns the identification of reliable earthquake precursors. Recently, some researchers have given rise to a re-examination process of dubious earthquake precursors and published their findings. For example Masci (2010, 2011a), by means of global geomagnetic Kp index time-series, demonstrated that many presumed magnetic seismogenic signatures are not related to the subsequent earthquakes but are normal variations driven by the geomagnetic activity level. More precisely, as pointed out by Masci (2011a, 2012a), since the Kp index is representative of the geomagnetic field average disturbances over planetary scale, we should not expect that a good correlation between an ULF parameter of the geomagnetic field and Kp will always and everywhere exist during a long-time range. On the contrary, if a close correspondence between these changes of an ULF geomagnetic field parameter and Kp exists during a period of time, this indicates that the changes are part of normal global geomagnetic field variations driven by solar-terrestrial interactions and cannot be described as earthquake-related signals. Here, some examples of questioned earthquake precursors are reported hoping to shed light on the usefulness of the ULF magnetic measurements to study the occurrence of pre-earthquake seismogenic signals. In addition, the results of the analysis of magnetic data from the Geomagnetic Observatory of L’Aquila during the period of the 2009 L’Aquila seismic sequence are reported as well

Brief communication “On the recent reaffirmation of ULF magnetic earthquakes precursors”

Hayakawa et al. (2009) and Hayakawa (2011) have recently reviewed some “anomalous” ULF signatures in the geomagnetic field which previous publications have claimed to be earthquake precursors. The motivation of this review is “to offer a further support to the definite presence of those anomalies”. Here, these ULF precursors are reviewed once again. This brief communication shows that the reviewed anomalies do not “increase the credibility on the presence of electromagnetic phenomena associated with an earthquake” since these anomalous signals are actually caused by normal geomagnetic activity. Furthermore, some of these ULF precursors have just been rebutted by previous publications

The INGV tectonomagnetic network: 2004?2005 preliminary dataset analysis

International audienceIt is well established that earthquakes and volcanic eruption can produce small variations in the local geomagnetic field. The Italian Istituto Nazionale di Geofisica e Vulcanologia (INGV) tectonomagnetic network was installed in Central Italy since 1989 to investigate possible effects on the local geomagnetic field related to earthquakes occurrences. At the present time, total geomagnetic field intensity data are collected in four stations using proton precession magnetometers. We report the complete dataset for the period of years 2004?2005. The data of each station are differentiated respect to the data of the other stations in order to detect local field anomalies removing the contributions from the other sources, external and internal to the Earth. Unfortunately, no correlation between geomagnetic anomalies and the local seismic activity, recorded in Central Italy by the INGV Italian Seismic National Network, was found in this period. Some deceptive structures present in the differentiated data are pointed out

NEOWISE observations of comet C/2013 A1 (Siding Spring) as it approaches Mars

The Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) mission observed comet C/2013 A1 (Siding Spring) three times at 3.4 {\mu}m and 4.6 {\mu}m as the comet approached Mars in 2014. The comet is an extremely interesting target since its close approach to Mars in late 2014 will be observed by various spacecraft in-situ. The observations were taken in 2014 Jan., Jul. and Sep. when the comet was at heliocentric distances of 3.82 AU, 1.88 AU, and 1.48 AU. The level of activity increased significantly between the Jan. and Jul. visits but then decreased by the time of the observations in Sep., approximately 4 weeks prior to its close approach to Mars. In this work we calculate Af\r{ho} values, and CO/CO2 production rates.Comment: 9 pages, 3 figures, accepted by Astrophysical Journal Letter