Ocean-Bottom Seismographs Based on Broadband MET Sensors: Architecture and Deployment Case Study in the Arctic.

Artem A Krylov,Grigory O Velichko,Daria D Rukavishnikova,Vladimir N Ivanov,Georgy K Timashkevich,Oleg Yu Ganzha,Igor P Medvedev,Elena A Radiuk,Konstantin A Roginskiy,Dmitry A Ilinskiy,Ivan V Egorov,Leopold I Lobkovsky,Alexander V Neeshpapa,Sergey A Kovachev,Igor P Semiletov,Mikhail A Novikov,Mikhail E Kulikov

doi:10.3390/s21123979

Abstract

The Arctic seas are now of particular interest due to their prospects in terms of hydrocarbon extraction, development of marine transport routes, etc. Thus, various geohazards, including those related to seismicity, require detailed studies, especially by instrumental methods. This paper is devoted to the ocean-bottom seismographs (OBS) based on broadband molecular–electronic transfer (MET) sensors and a deployment case study in the Laptev Sea. The purpose of the study is to introduce the architecture of several modifications of OBS and to demonstrate their applicability in solving different tasks in the framework of seismic hazard assessment for the Arctic seas. To do this, we used the first results of several pilot deployments of the OBS developed by Shirshov Institute of Oceanology of the Russian Academy of Sciences (IO RAS) and IP Ilyinskiy A.D. in the Laptev Sea that took place in 2018–2020. We highlighted various seismological applications of OBS based on broadband MET sensors CME-4311 (60 s) and CME-4111 (120 s), including the analysis of ambient seismic noise, registering the signals of large remote earthquakes and weak local microearthquakes, and the instrumental approach of the site response assessment. The main characteristics of the broadband MET sensors and OBS architectures turned out to be suitable for obtaining high-quality OBS records under the Arctic conditions to solve seismological problems. In addition, the obtained case study results showed the prospects in a broader context, such as the possible influence of the seismotectonic factor on the bottom-up thawing of subsea permafrost and massive methane release, probably from decaying hydrates and deep geological sources. The described OBS will be actively used in further Arctic expeditions.

Highlights

Seismic hazard assessment and seismic zonation are extremely important and are among the most complicated problems of seismology
The lack of knowledge applies to geohazards related to seismicity, such as soil liquefaction, underwater landslides, tsunamis, massive methane seepage from the sea bottom, etc
Numerous geohazards could be related with progressive methane release, including impact on infrastructure of the Northern Sea Route, gas and oil under-water pipes, and general gas and oil exploration

Summary

Introduction

Seismic hazard assessment and seismic zonation are extremely important and are among the most complicated problems of seismology. The purposes of the present paper are to introduce the architecture of several modifications of the OBS based on broadband molecular–electronic transfer (MET) sensors and to demonstrate their applicability in solving different seismic hazard assessment tasks. The force feedback mechanism is provided by an interaction of the magnet with a current ment, the vertical sensors of CME-4111 seismometers are not equipped with a force feedback as well This was done intentionally to achieve the lowest power consumption. Another device is a RBR virtuoso3D wave logger [23], equipped with a Keller pressure sensor, which is based on the use of a piezoelectric quartz sensor as a baro-sensitive element It records the pressure values of the water column and translates them into the variable depth of the location.

OBS Modification for Deep Waters

Temperature Sensors AD8218 sensor

Recording of Ambient Seismic Noise in the Laptev Sea

Registration of the Teleseismic Signals

Registration of the Signals from Local Earthquakes