The Alaska Transportable Array: As Built

Abstract

Abstract Alaska is the last frontier and final destination for the National Science Foundation-supported EarthScope USArray Transportable Array (TA) project. The goal of this project is to record earthquakes and image the structure of the North American continent. The Alaska TA consists of 283 broadband seismic stations evenly spaced about 85 km apart to cover the state of Alaska and into western Canada. The sensor emplacement technique and station design were developed specifically for superior performance—both in terms of seismic noise levels and station durability. This technique and design were used for the 194 new stations installed as well as the 32 existing broadband stations that were upgraded. Trial stations were installed in 2011–2013 as part of a process to test and refine the installation design. The main deployment began in 2014 using the final station design and was completed in 2017. From 2018 through 2020, Incorporated Research Institutions for Seismology (IRIS) operated the Alaska TA by performing servicing, station improvements, and data quality monitoring. High data return was maintained throughout, though some stations had lower real-time data delivery in winter. 110 TA stations are expected to transition to other operators in 2019 and 2020, and the data from these are openly available under new network codes. The last 84 stations are expected to be removed during the 2021 field season to close out the TA project. The Alaska TA was installed safely despite a challenging environment and has been operated to maximize the continuity and quality of data collected across a vast geographic region, enabling exciting scientific research for years to come.