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In this study, we investigated correlations between electromagnetic and seismic signals of the 2017 February 15 Veracruz, Mexico, earthquake (M w = 4.8). We carried out a time–frequency misfit analysis based on the continuous wavelet transform in order to compare electric, magnetic and seismic records accurately. This analysis was performed for horizontal and vertical components separately. Our results from time–frequency misfit and goodness-of-fit criteria confirm the general similarity between seismic and electromagnetic signals both in frequency and time. Additionally, we studied the behaviour of peak amplitudes of seismoelectromagenetic records as a function of magnitude and distance. Our observations are in good agreement with previous studies, confirming scaling with magnitude and attenuation with distance. Radiated seismic energy estimations were performed with two methods: integration of velocity records and empirical Green function, respectively. Estimated energy magnitudes (4.35 <  M e < 4.98) are consistent with reported seismic magnitudes for this event. We propose a method for determining electric and magnetic coseismic energies based on the concept of energy flux as implemented in the frequency domain by the integration of electromagnetic records. The calculated energies showed that the radiated seismic energy is much higher than the electric and magnetic energies. [ABSTRACT FROM AUTHOR]

The largest-magnitude slow slip events (SSEs) in the world are found to invade the seismogenic zone in the Guerrero seismic gap in Mexico. The Guerrero SSEs repeat within the same region every 4 yr. Here we examine the geological and geophysical evidence for the mechanism that allows for transient slip in the gap and at no other point along the >1000-km-long subduction zone. We find that longlasting past magmatic activity most likely produced an impermeable gabbroic layer in the lower crust within the gap. This body has acted as a seal to trap fluids and over-pressurize the plate interface, thereby generating a transient slip region allowing for SSEs to invade the seismogenic zone. This suggests that transient slip can occur in typically seismogenic regions, but requires special conditions. It also adds to the growing evidence that the Guerrero gap may have a lower seismic hazard compared to the rest of the coast, which is opposite to what is reported by government agencies. [ABSTRACT FROM AUTHOR]