Variations of geomagnetic cutoff rigidity in the southern hemisphere close to 70°W (South-Atlantic Anomaly and Antarctic zones) in the period 1975–2010

Cordaro, E. G.; Venegas-Aravena, Patricio; Laroze, David

doi:10.1016/j.asr.2018.12.019

Cited by 9 publications

(10 citation statements)

References 26 publications

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“…This is the combined result of the reduction of the main dipole component of the magnetic field as well as the additional displacement of the effective magnetic center from Earth's geo-center. Researchers in South America [8] are studying the effects of these changes by establishing specific cosmic ray and geomagnetic observatories. Also note that there is a region of decreasing cutoff rigidity in central Asia with a "mirror" region of increases in the same longitude region in the Indian Ocean.…”

Section: Pos(icrc2019)1154 Pos(icrc2019)1154mentioning

confidence: 99%

Vertical Geomagnetic Cutoff Rigidities for Epoch 2015

Smart¹,

Shea²

2020

Proceedings of 36th International Cosmic Ray Conference — PoS(ICRC2019)

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Section: Pos(icrc2019)1154 Pos(icrc2019)1154mentioning

confidence: 99%

Vertical Geomagnetic Cutoff Rigidities for Epoch 2015

Smart¹,

Shea²

2020

Proceedings of 36th International Cosmic Ray Conference — PoS(ICRC2019)

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“…The first significant property in the secular variation of the geomagnetic field is determined by the shielding it exercises on the cosmic ray particles which reach the Earth, called the geomagnetic cutoff rigidity. It is defined as the product of the force of the magnetic field and the curvature radius of the incident particle rg, which relates the geomagnetic latitude with the classification of the particle trajectories and could be related to geological features in the Chilean margin [Pomerantz, 1971, Shea and Smart, 2001, Smart and Shea, 2005, Cordaro et al, 2018, Cordaro et al, 2019.…”

Section: Observatories Of Geomagnetic Data and Magneto-seismic Relationmentioning

confidence: 99%

Analysis of geomagnetic measurements prior the Maule (2010), Iquique (2014) and Illapel (2015) earthquakes, in the Pacific Ocean sector of the Southern Hemisphere

Cordaro

Venegas-Aravena

Laroze

2019

Preprint

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Abstract. It has been possible to detect variations in the vertical component of the geomagnetic field (Bz) through its first and second derivate in a range of frequencies (microHz); these seem to be roughly related with some major seismic subduction events. We studied the period 2010–2015, analysing the daily values of magnetic records over periods close to the last three significant events that occurred through the Chilean margin, i. e., along a boundary between convergent plates that is characterized by the occurrence of seismic events of magnitude greater than Mw8. These are the events of Iquique 2014, Illapel 2015 and Maule 2010, all at different latitudes, on different dates and characterized by different types of margin (erosive or accretionary). Certain similarities were found in the associated magnetic field variations: 1) Variation in the radial or z component of the geomagnetic field and its first and second temporal derivative, modelled as a small jump, and small oscillations in the second derivative, generating a frequency band between 1c / 48.9 hours and 1c / 79.13 Hrs. 2) A variable time lapse of between 30 and 120 days; and 3) The seismic event. Furthermore, when analysing spectrograms for the second temporal derivate of the radial component, different behaviour is found related to its spectral density. This takes the form of an increase in ultra-low frequencies (0.01–0.4 mHz) between the start of the magnetic jump and the seismic event. These frequencies are lower than those found during the last years by research groups that related magnetic field and earthquakes, furthermore the concept of time lapse close to 30 days is in agreement with those research groups. The previous analyses may not be so robust, this is why additionally a new method is used with stations closer to the events and time periods of two years. We analysed the daily cumulative number of anomalous behaviour in z component of magnetic field on ground based magnetometers. The results show an increase in the number of magnetic anomalies prior to the occurrence of the three earthquakes. The behavior of the anomalies is similar to those presented by other authors for other earthquakes with similar methods in ionosphere. All this magnetic features might recover seismic information of the events and could be related with Lithosphere-Atmosphere-Ionosphere Coupling.

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“…Thus, the secular variation of the magnetic field can be interpreted as the response of the movement of the fluid outer core interacting with the topography of the lower mantle. Then, as that topography in the core-mantle boundary corresponds to a projection of the topography of the earth's surface (Soldati et al, 2012), it was not surprising that Cordaro et al (2018) and Cordaro et al (2019) found significant variations of geomagnetic cutoff rigidity Rc at relevant geological places in the Chilean margin.…”

Section: Introductionmentioning

confidence: 99%

Long-term magnetic anomalies and its possible relationship to the latest Greater Chilean earthquakes in the context of the seismo-electromagnetic theory

Cordaro¹,

Venegas-Aravena²,

Laroze³

2020

Preprint

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Abstract. Several magnetic measurements and theoretical development from different research groups have shown certain relationship with worldwide geological processes. Secular variation of geomagnetic cut off rigidity, magnetic frequencies, or magnetic anomalies have been linked with spatial properties of active convergent tectonic margin or earthquakes occurrences during recent years. These include the rise of similar fundamental frequencies in the range of micro hertz before Maule 2010, Japan 2011, and Sumatra 2004 earthquakes and the dramatic rise of the cumulative number of magnetic anomalous peaks before several earthquakes as Nepal 2015 and Mexico 2017, among others. Currently, all of these measurements have been physically explained by the microcrack generation due uniaxial stress change in rock experiments. The basic physics of these experiments have been used to describe the lithospheric behavior in the context of the seismo-electromagnetic theory. Due to the dramatic increase in experimental evidence, physical mechanism and theoretical framework, this paper analyses vertical magnetic behavior close to the latest three main earthquakes in Chile: Maule 2010 (Mw8.8), Iquique 2014 (Mw8.2), and Illapel 2015 (Mw8.3). The FFT, Wavelet transform and daily cumulative number of anomalies methods were used during quiet space weather time during one year before and after each earthquake in order to filter space influence. FFT Method confirm the raise of power spectral density in mHz range before one month each earthquake, which decrease to lower values after some months after earthquake occurrence. The cumulative anomalies method exhibited and increase previous to each Chilean earthquake (50–90 days prior earthquakes) similar to those found for Nepal 2015 and Mexico 2017. The wavelet analyses also show as similar properties as FFT analysis. However, the lack of physics-based constrain in the wavelet analysis do not allow conclusion as strong as FFT and cumulative methods. By using these results and previous research, it could be stated that these magnetic features could give seismic information from impending events. Additionally, these results could be related to the Lithosphere–Atmosphere–Ionosphere coupling (LAIC effect) and the growth of micro cracks and electrification in rocks described by the seismo-electromagnetic theory.

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Variations of geomagnetic cutoff rigidity in the southern hemisphere close to 70°W (South-Atlantic Anomaly and Antarctic zones) in the period 1975–2010

Cited by 9 publications

References 26 publications

Vertical Geomagnetic Cutoff Rigidities for Epoch 2015

Vertical Geomagnetic Cutoff Rigidities for Epoch 2015

Analysis of geomagnetic measurements prior the Maule (2010), Iquique (2014) and Illapel (2015) earthquakes, in the Pacific Ocean sector of the Southern Hemisphere

Long-term magnetic anomalies and its possible relationship to the latest Greater Chilean earthquakes in the context of the seismo-electromagnetic theory

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