Lineament analysis as a seismic precursor:The El Mayor Cucapah earthquake of April 4,2010(MW7.2),Baja California,Mexico

An earthquake called the MW7.2“El Mayor Cucapah”earthquake on April 4,2010 has been analyzed for seismic precursor.The changes in the lineament system concerning its pattern and time intervals were analyzed during the earthquake preparation period and occurrence using the automated lineament detection method.The Landsat 5 TM images were processed using LESSA and ADALGEO software obtaining similar results.The statistical analysis revealed the stress accumulation due to plate interaction during earthquake formation.The study shows that the number of extracted lineaments changes rapidly about 23 months before the earthquake,and the systems return to the initial stage after 23 months.Most lineaments coincide with the extension of the San Andreas Fault as NW direction is the dominant trend.Thus,it can be concluded that the featural changes within the Rose diagram corresponding to the different strokes direction along with oriented elongation lines as disclosed in the present study using satellite images could be identified as a mid-term and/or short-term precursors of the earthquake.However,even though the dynamism of the El Mayor Cucapah earthquake is found in the extracted lineaments,it is possible to isolate more significant earthquakes even if new ones appear near the zone.Moreover,using two algorithms for lineament detection allows for the tectonics to corroborate the obtained lineaments and dynamism.

Quality assessment of Continuous Operating Reference Stations(CORS)-GPS stations in Mexico

The present analysis provided the quality assessment of 65 Continuous Operating Reference Stations(CORS) situated in and around Mexico using the data of about ten years(January 2010 to January 2020).To accomplish the assessment,we considered 4 quality indexes for performing the quality check,incluing the multipath effect on L1 and L2 bands,signal-to-noise ratio in both bands,cycle slips,and integrity.Meanwhile,a new reference parameter named regio nal values for Mexico(RVM) was calculated for the stations situated in Mexico.Additionally,an exhaustive analysis of the quality indicators in the worst and best cases was performed.The signal degradation was proved by a long-term time series and cru stal defo rmation analysis in GAMIT/GLOBK platform.The results showed a stro ng correlation between integrity,cycle slips and daily observations time,and the multipath effect is strong in the case of outdated systems.The study indicates that the estimated quality indexes and values could be the basis for establishing new CORS in Mexico,and the errors corrections which cannot be mitigated in the postprocessing stage would greatly help utilize the data for different scientific applications.The results were supported by deformation analysis in part of Baja California Peninsula in Mexico indicating northern and eastern velocity vector of -3.08±0.02 mm/yr,-7.85±0.02 mm/yr and-0.07±0.03 mm/yr,-9.33±0.02 mm/yr respectively at MPR1 and INEG stations.