TY - JOUR

T1 - High precision measurements of absolute gravity in Mexico

T2 - The jalisco block changes in gravity triggered by distant earthquakes

AU - Esparza, Alfredo

AU - Arzate, Jorge

AU - Timmen, Ludger

AU - Silliker, Jason

AU - Schilling, Manuel

N1 - Funding information: We acknowledge the financial support from PAPIIT, project IN116816, to carry out the JB measurements. We are grateful to Josefina Jacobo and Gina Villalobos (UT3-CICESE in Tepic), to Araceli Zamora of the University of Guadalajara, campus Puerto Vallarta, to Norma Barocio and Jorge Vega (Chamela station, IB-UNAM), to Ramón Sosa and colleagues (CUNIVO, UC-Manzanillo), to the authorities of the Institute of Astronomy of the U. of Guadalajara, and to Raúl Gómez from the INEGI in Aguascalientes for providing facilities during the AG acquisition campaigns. We greatly appreciate the assistance of Calixto Morales and Fernando Martínez during the measuring campaigns in the JB. Particularly, we would like to thank Dan Winester of NOAA, and Roger Billham from the University of Colorado at Boulder who kindly sheared their unpublished data. PTB Braunschweig funded logistical costs (travelling and freight shipping) of the LUH team and instrumentation to Mexico. We thank the anonymous referees thatehlepd to improvehtismnuscripat. We acknowledge the financial support from PAPIIT, project IN116816, to carry out the JB measurements. We are grateful to Josefina Jacobo and Gina Villalobos (UT3-CICESE in Tepic), to Araceli Zamora of the University of Guadalajara, campus Puerto Vallarta, to Norma Barocio and Jorge Vega (Chamela station, IB-UNAM), to Ramón Sosa and colleagues (CUNIVO, UCManzanillo), to the authorities of the Institute of Astronomy of the U. of Guadalajara, and to Raúl Gómez from the INEGI in Aguascalientes for providing facilities during the AG acquisition campaigns. We greatly appreciate the assistance of Calixto Morales and Fernando Martínez during the measuring campaigns in the JB. Particularly, we would like to thank Dan Winester of NOAA, and Roger Billham from the University of Colorado at Boulder who kindly sheared their unpublished data. PTB Braunschweig funded logistical costs (travelling and freight shipping) of the LUH team and instrumentation to Mexico. We thank the anonymous referees that helped to improve this manuscript.

PY - 2020/7/1

Y1 - 2020/7/1

N2 - We report the results of 16 Absolute Gravity (AG) measurements distributed central and western Mexico employing two free-fall gravity instruments; the FG5X-220 of Leibniz Universitat Hannover (LUH), and the FG5X-252 instrument of the Centro Nacional de Metrologia (CENAM). Previous to the setup of new stations and acquisition campaigns, the FG5X-252 was certified in two steps, first a mutual comparison with the reference gravimeter FG5X-220, which have a long range stability below 2 μGal, and later through an international comparison at NOAAs Table Mountain, Col. facilities with 13 other instruments of different countries. The acquisition campaigns in the Jalisco Block (JB) took place during the dry season of 2016 and 2018, which included AG stations in Chamela (CHA), Guadalajara (AGG), Manzanillo (MAN), Puerto Vallarta (UGP), and Tepic (TEP); the later established new reference station in the north of the JB in 2016. The results obtained from the 2016 and 2018 field campaigns in the JB were compared with 1996 AG data acquired by NOAA at the same sites established. The observed vertical displacements in the two years period at stations CHA (+22.7 cm), UGG (+44.3 cm) and MAN (+54.6 cm) overcomes substantially the annual average (2.8 cm, 4.2 cm y 3.6 cm respectively) from the difference of the AG measurements 2016-1996. In the same period the UGP station subsided 8.5 cm, while station TEP remained quite stable (-0.25). In September 2017 two large earthquakes of magnitudes 8.2 and 7.1 occurred in the coast of Chiapas (07/Nov/2017) and in the State of Puebla (19/Nov/2017), which were recorded at some of the UNAVCOs GPS stations, namely MAN, UGG and CHA even though the nearest seismic source was located more than 500 km to the east. The analysis of our results in combination with other geophysical data support the hypothesis that the earthquake with epicenter in Puebla triggered the aseismic subduction of a segment of the Ribera Plate (RP), which in turn uplifted the stations above mentioned. We conclude that the aseismic subduction in this region is facilitated by a wet oceanic crust that carries important amounts of marine sediments, producing a lubricated interface between oceanic RP and the overriding JP.

AB - We report the results of 16 Absolute Gravity (AG) measurements distributed central and western Mexico employing two free-fall gravity instruments; the FG5X-220 of Leibniz Universitat Hannover (LUH), and the FG5X-252 instrument of the Centro Nacional de Metrologia (CENAM). Previous to the setup of new stations and acquisition campaigns, the FG5X-252 was certified in two steps, first a mutual comparison with the reference gravimeter FG5X-220, which have a long range stability below 2 μGal, and later through an international comparison at NOAAs Table Mountain, Col. facilities with 13 other instruments of different countries. The acquisition campaigns in the Jalisco Block (JB) took place during the dry season of 2016 and 2018, which included AG stations in Chamela (CHA), Guadalajara (AGG), Manzanillo (MAN), Puerto Vallarta (UGP), and Tepic (TEP); the later established new reference station in the north of the JB in 2016. The results obtained from the 2016 and 2018 field campaigns in the JB were compared with 1996 AG data acquired by NOAA at the same sites established. The observed vertical displacements in the two years period at stations CHA (+22.7 cm), UGG (+44.3 cm) and MAN (+54.6 cm) overcomes substantially the annual average (2.8 cm, 4.2 cm y 3.6 cm respectively) from the difference of the AG measurements 2016-1996. In the same period the UGP station subsided 8.5 cm, while station TEP remained quite stable (-0.25). In September 2017 two large earthquakes of magnitudes 8.2 and 7.1 occurred in the coast of Chiapas (07/Nov/2017) and in the State of Puebla (19/Nov/2017), which were recorded at some of the UNAVCOs GPS stations, namely MAN, UGG and CHA even though the nearest seismic source was located more than 500 km to the east. The analysis of our results in combination with other geophysical data support the hypothesis that the earthquake with epicenter in Puebla triggered the aseismic subduction of a segment of the Ribera Plate (RP), which in turn uplifted the stations above mentioned. We conclude that the aseismic subduction in this region is facilitated by a wet oceanic crust that carries important amounts of marine sediments, producing a lubricated interface between oceanic RP and the overriding JP.

KW - Absolute gravity

KW - Aseismic subduction

KW - International comparison

KW - Jalisco block

KW - Vertical displacements

UR - http://www.scopus.com/inward/record.url?scp=85090845488&partnerID=8YFLogxK

U2 - 10.22201/igeof.00167169p.2020.59.3.2091

DO - 10.22201/igeof.00167169p.2020.59.3.2091

M3 - Article

AN - SCOPUS:85090845488

VL - 58

SP - 155

EP - 168

JO - Geofisica Internacional

JF - Geofisica Internacional

SN - 0016-7169

IS - 3

ER -