====== Site selection ======

  * Seismic noise: include long term variations. 
 Previous short term studies:

{{:et_update_2017:short_term_beker_et_al_2015.png?800|}} 
 
 Recent long term measurement, preliminary, Sos Enattos, 480 days:

{{:et_update_2017:sardinia_long_term_noise.png?800|}}

Further info: [[https://mydrive.kfki.hu/f/7010f295a0/]] and [[https://mydrive.kfki.hu/f/7aee233cf4/]]
  * Geotechnical baseline report (use industry standard): important for tunnel construction (to reduce risks) and gives also info about subsurface for NN estimates
    * Water levels, avoid old mines, human activities (cities), future infrastructure plans in region
  * Realistic sub-surface model to get NN curve (provided by GW scientists)
    * Include NN reduction in ET curve
    * Requires surface and borehole measurements
  * Estimate construction costs
  * Environmental impact study
    * Communicate with local entities & society 
  * Need local support: academia, political, funding agencies, industry, infrastructure (airport), local knowledge to build ET, local government
  * Electromagnetic noise – Schumann resonance (ionosphere): low frequency part of the Earth’s EM field spectrum
  * Propose 2 or 3 sites to ESFRI
  * Rules for partner countries and host country (s)
    * Host country pays ‘good’ % of the ET project
  * Involve CERN:  
    * Use their expertise in vacuum, cryogenics, tunnel construction, financing
    * Show that we studied the option to build ET at CERN

====== Seismic sensors ======

  * Calibrate seismic sensors or use industry standard equipment
  * Frequencies below the cut-off frequency of ET are important because of up-conversion
    * Frequency band seismic sensors: 0.1 -100 Hz

====== Other remarks ======

  * Sensitivity curve – low frequency cut-off  will be derived from the ET science case
  * Self-noise: enforce rules based on Ligo/Virgo experience
  * Relaxation/deformation of the site: prediction if possible, monitoring in any case


====== Summary ======

  * Complex preparation
  * __Scientific:__ Long term seismic characterization, electromagnetic noise  
  * __Technical:__ geological baseline report, environmental impact study, construction costs, ...
  * __Social, political:__ local support, governmental roles, CERN

====== To do ======

  * Continue/start measurements and develop some comparable criteria -- geophysics
  * Prepare the rules