Design and Implementation of a Prototype Seismogeodetic System for Tectonic Monitoring

Abstract

This manuscript describes the design, development, and implementation of a prototype system based on seismogeodetic techniques, consisting of a low-cost MEMS seismometer/accelerometer, a biaxial inclinometer, a multi-frequency GNSS receiver, and a meteorological sensor, installed at the Doñana Biological Station (Huelva, Spain) that transmits multiparameter data in real and/or deferred time to the control center at the University of Cadiz. The main objective of this system is to know, detect, and monitor the tectonic activity in the Gulf of Cadiz region and adjacent areas in which important seismic events occur produced by the interaction of the Eurasian and African plates, in addition to the ability to integrate into a regional early warning system (EWS) to minimize the consequences of dangerous geological phenomena.

Keywords: earth deformation; seismic hazard; seismogeodetic systems; tectonic surveillance; time series analysis; tsunami hazard.

Figure 1

Instrumentation located in the Doñana National Park, Huelva, Spain: (A) the prototype seismogeodetic system, (B) metal tripod that supports the Leica Geodetic (AR10) antenna, Leica GNSS receiver, and weather sensor, (C) box containing the GNSS receiver and main communication switch, (D) Vaisala weather sensor (WXT520), (E) concrete chamber located 1m away from the tripod, (F) Leica GR30 GNSS receiver, (G) contents of the concrete chamber: Seismometer, Inclinometer, communications connectors, power supply connectors, and desiccant bags that prevent humidity, (H) GNSS receiver UBX–M8030, (I) Raspberry Shake 4D Seismometer/Accelerometer, (J) Biaxial Digital Tilt Logger DTL202B, and (K) Vaisala weather sensor, owned by AEMET.

Figure 2

Network diagram and hardware components of the prototype seismogeodetic system (communications, sensors, servers, virtual machines, NAS, mirror backup, etc.); it is divided into three parts: Prototype Seismogeodetic (Doñana Station), UCA–HUB, and Control Center (LAGC). Initially, the prototype, and the UCA–HUB are interconnected by the VPN service provided by the CSIC, facilitating data transmission over the Internet to the management and control center, which has a Citrix XenServer virtual infrastructure with virtual machines that have services and applications dedicated to the automatic acquisition, processing, visualization, and filtering of data produced.

Figure 3

Structure of the components involved in the implementation of the prototype; it is divided into two groups and three subgroups that show the components of hardware, services, communications, and virtual infrastructure of the control center (LAGC–UCA), and Doñana Station, as well as the virtual machines that contain the acquisition, processing, and filtering modules.

Figure 4

Results (E, N, U) of the DONA station time series; the GNSS processing was performed with the BERNESE 5.2 software using ITRF14. This figure shows the time series with the linear fit and the CATS filter, as well as the velocities per component.

Figure 5

Results (E, N, U) of the DONA station time series; the GNSS processing was performed with the BERNESE 5.2 software using ITRF14. In addition, Kalman and Wavelets filters were applied.

Figure 6

Seismogram with a simulation of a seismic event (EHZ, ENE, ENN, and ENZ components) to know the resolution of Raspberry Shake RS4D seismometer/accelerometer and check the quality of the generated data.

Figure 7

Seismic events display on SEISAN 12.0 software for seismic analysis. (A) Seismogram of the earthquake that occurred at 22:03:49 on 1 January 2022, recorded on Z channel of the RS4D seismometer with a filter of 2–15 Hz. (B) Unfiltered seismogram of the same event with the waves phases P and S, and coda selected. (C) Signal amplification, and impulsive arrival of the P-wave and arrival of the S-wave.

Figure 8

Map showing the geodynamic context, seismic activity (2015–2022), and main faults of the southern region of the Iberian Peninsula and North Africa. The most important faults are Gorringe Bank Region, Gulf of Cadiz (GC), Azores–Gibraltar Fault, Saint Vincent Cape (SVCP), Alboran Sea, Betic Mountain Ranges, Eastern Betic Shear Zone (EBSZ), Trans-Alboran Shear Zone (TASZ), Horseshoe Abyssal Plain (HAP), Horseshoe fault (HF), São Vicente Canyon (SVC), Guadalquivir Bank (GVB), and Marquês de Pombal Fault Block (MPFB). In addition, clusters A, B, C, and D are shown, which reflect the concentration and distribution of the seismic epicenters.

Figure 9

Map showing the location of the 4.4 Mw earthquake that occurred on 1 January 2022 in the Gulf of Cadiz (Lat: 36.3276, Lon: −7.6271, depth: 6 km) recorded by the RS4D seismometer/accelerometer. We also show seismic events of different magnitudes that occurred between 2005 and 2022 in the Gulf of Cadiz and adjacent areas (data taken from the public seismic catalog of IGN), the location of the Seismogeodesic System in the Doñana Biological Station, Huelva, Spain, the Control Center (LAGC–UCA), and the focal mechanism produced by the studied earthquake (A).

Figure 10

Seismogram (A) and spectrogram (B) of the earthquake that occurred on 1 January 2022 at 22:03:49 registered by the RS4D seismometer/accelerometer integrated in the prototype. In this seismic signal, a low signal-to-noise ratio was found in certain periods of time, which allowed the use of a first filter of 0.5 Hz to 10 Hz and a later one of 2 Hz to 8 Hz.

Figure 11

East, North, and Vertical components of the GNSS-GPS time series (1 Hz sample rate) for the position of the GR30 GNSS receiver seconds after the magnitude 4.4 Mw earthquake of 1 January 2022, with epicenter about 130 km southwest of Doñana, Huelva, Spain. A small change in the trend is shown 45 s (approximately) after the event occurred; this corresponds to the arrival of the seismic wave.

Figure 12

Inclinometry results (30 s sample rate) where the displacement produced in both sensors (Tilt 1, Tilt2) is observed and that corresponds to the arrival of the seismic wave of the 4.4 Mw earthquake that occurred on 1 January 2022 in the gulf of Cadiz.

Figure 13

Accelerographic signals from the ALMT (Almonte) station corresponding to the 5.4 Mw earthquake that occurred on 14 August 2022 in the Gulf of Cadiz.

Figure 14

Accelerographic signals from the LEPE station corresponding to the 5.4 Mw earthquake that occurred on 14 August 2022 in the Gulf of Cadiz.