Determination of the onset time in polarization power ratio Z/H for precursor of Sumatra earthquake

Abstract

Abstract. Determination of onset time precursors of strong earthquakes (Mw > 5 ) and distance (d < 500 km ) using geomagnetic data from Geomagnetic station KTB, Sumatra and two station references DAV, Philippine and DAW, Australia. separate techniques are required in its determination . Not the same as that recorded in the kinetic wave seismograms can be determined by direct time domain. Difficulties associated with electromagnetic waves seismogenic activities require analysis of the transformed signal in the frequency domain. Determination of the frequency spectrum will determine the frequency of emissions emitted from the earthquake source. The aim is to analyze the power amplitude of the ULF emissions in the horizontal component ( H ) and vertical component ( Z ). Polarization power ratio Z / H is used for determining the sign of earthquake precursors controlled by the standard deviation. The pattern recognition polarization ratio should be obtained which can differentiate emissions from seismogenic effects of geomagnetic activity. ULF emission patterns generated that seismogenic effect has duration > 5 days and the dominance of emission intensity recorded at the Z component and for the dominance of the emission intensity of geomagnetic activity recorded in the component H. The result shows that the onset time is determined when the polarization power ratio Z / H standard deviation over the limit ( p ± 2  ) which has a duration of > 5 days .

ULF geomagnetic anomaly associated with the Sumatra-Pagai Islands earthquake swarm during 2020

“…1 and Table 1. Ahadi et al (2014) stated that ULF anomalies related to earthquakes with a magnitude of > 5 can still be detected at observation station with a distance of ≤ 500 km from the earthquake source. Of six earthquakes studied, five earthquakes were foreshock earthquakes with a thrust fault mechanism caused by plate subduction in the megathrust zone, Mentawai-Pagai, while the earthquake on November 17, 2020 (M W = 5.9) was a shallow earthquake due to the fault activity in investigated fracture zone around the plate collision boundary, which has a strike-slip fault movement mechanism.…”

“…The disturbance storm index (Dst) is used as validation to ensure that the anomaly source is not external disturbances such as geomagnetic activity. The impact of external disturbances such as geomagnetic storms will more significantly affect the intensity of the horizontal component of the geomagnetic signal (H) rather than the vertical component (Z) (Ahadi et al, 2014). The Dst index is also used to observe geomagnetic activity recorded in the equatorial and low latitude areas (Saroso et al, 2009).…”

Experimental thermal time estimation for Mach‐Zehnder interferometer to study coupled heat and mass transfer

“…MZI has been found to be an accurate and precise experimental model to monitor thermodiffusion inside a parallelepiped cavity (also identified as a cell) when a thermal gradient is applied across two parallel sides. [21][22][23] Processing the results of this experiment requires determining the stage of the experiment during which temperature variations cause the refractive index of the mixture to change, known as thermal time, and the phase that refractive index changes are due to the separation of the components, which is called diffusion, or the thermodiffusion phase. We can separate these two phases according to the theoretical thermal time of the liquid mixture.…”