DMC: Knowledge Base: Question: Do you see Earth tides on the USArray TA stations?

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Do you see Earth tides on the USArray TA stations?

webmaster  staff  Nov. 14, 2013, 1:53 p.m.

Do you see Earth tides on the USArray TA stations?


Gillian Sharer gravatar

Gillian Sharer  accepted answer  staff  Nov. 14, 2013, 1:54 p.m.

Earth tides can be seen at most of the coastal TA stations using an appropriate filter. Very long period noise, siting far inland, and/or vault instabilities at a site are possible reasons why Earth tides may not be observed. See the attached images for more information, which compare an earth tide signal signature on the LHZ channel at GSN network station KDAK on Kodiak Island, Alaska, USA with an earth tide signal signature on the LHZ channel at TA station I64A at Boothbay, Maine, USA. Both signals have been demeaned and have a low-pass filter applied.

II_KDAK_LHZ

Figure 1: Earth tide signal signature at GSN station KDAK on Kodiak Island, Alaska, USA.

TA_I64A_LHZ

Figure 2: Earth tide signal signature at TA station I64A at Boothbay, Maine, USA.

Figure 3 below shows this in even more detail for station TA_I64A on the LHZ channel:

TA_I64A_LHZ comparison

Figure 3: Although the seismometers used by TA have a corner frequency of X Hz (1/X sec period) (0.02/50), the faint strength of tidal signals is still above the instrument noise and easily visible when the data have been low pass filtered below 1000 sec periods.