TAAC approves of IRIS’ plans for dealing with the battery system problem by testing a replacement part and following a timeline for the decision of how to prepare site enclosures for next year. This will result in a mix of AGM-only and Lithium installations for next year. If power woes at stations are serious, we repeat our recommendation that delayed data is better than fractional data, which is better than no data. If it becomes necessary to suspend data downloads at a site to ensure more complete data collection, then we support that choice.
TAAC supports the inclusion of additional strong motion (40 sps) and infrasound (20 sps) real-time data streams, up to the limit IRIS can afford given the structure of its BGAN contract.
TAAC recommends that IRIS include in its all-hands meeting or in another venue a frank and open discussion about what went well, what worked efficiently, and anything that did not go so well or where efficiency can be gained. It is important to make sure that any avoidable incidence of wasted time or inefficiency be identified so that plans can be adjusted for the coming years. We strongly recommend that all site installations on the southern part of the network be deployed, even if that means losing a few more sites at the northern or western limits.
TAAC recommends that assessments of the data usage be made next year, ideally compiled using existing DMC tools
TAAC recommends that IRIS produce a curated data volume for the Lower 48 TA stations, and distribute it to interested users in an efficient way for a reasonable cost of reproduction.
TAAC recommends that AK TA station demobilization should begin in 2020, and site removals be split as evenly as possible between 2020 and 2021. Efficiency and cost should be the determining factors in deciding the order of demobilization, rather than site location or site installation date. Even accounting for potential winter data loss, this should ensure 18-24 months of recording as a full array, and some individual stations will have much longer data spans. If station demobilization were to begin earlier, then additional factors would have to be considered as some stations might have as little as a year of operation at the beginning of demobilization; an earlier demobilization date would probably also require something like a 30%/70% split between the two years, which would be a significant challenge in the heavy year. We feel that the 2020/2021 demobilization plan has significant advantages.
TAAC fully supports an amphibious array complement to the TA. The larger aperture of the array would be most important for extending the capability of the TA to image the mantle beneath the active southern Alaska margin. Thus the TAAC supports a larger aperture OBS network during the overlap with the TA, including the back-arc region and filling in gaps in the TA caused by Bristol Bay and southern Bering Sea. TAAC also encourages more complete operation of the Alaska Volcano Observatory seismic networks, although these fall under the responsibility of the USGS and not IRIS or NSF.
IRIS should make arrangements to save and bring back cuttings from bedrock drilling for TA sites so that these samples may be used for a variety of geological studies, including geochronology. Cuttings mean chips and pieces, with no expectation of complete core or oriented samples. A number of geologists have expressed interest in cooperation and this group could be used to make recommendations for usage of the samples. Samples could be stored in the Alaska Geological Materials Center (http://dggs.alaska.gov/gmc/general-info.php).