" they have little or no effect on seismic phenomena"


From the National Oceanic and Atmospheric Administration.""Local wind and weather patterns also can affect tides. Strong offshore winds can move water away from coastlines, exaggerating low tide exposures. Onshore winds may act to pile up water onto the shoreline, virtually eliminating low tide exposures. High-pressure systems can depress sea levels, leading to clear sunny days with exceptionally low tides. Conversely, low-pressure systems that contribute to cloudy, rainy conditions typically are associated with tides than are much higher than predicted."
1)Therefore high pressure and low pressure systems modify the hydrostatic head of a column of seawater.
2)Low pressure can generate intense storms containing abundant energy leading to exaggerated tides,surges and wave action.
3)All these activities generate seismic noise
4)if the magnitude of the noise due to the above exceeds the failure point of adjacent stressed rocks failure will occur.
5)The failure may be seen as microseismic events or could be larger. This would depend on the nature of the system and the forces acting on it

Rock stress
http://dc-app3-14.gfz-potsdam.de/pub/guidelines/WSM_analysis_guideline_breakout_image.pdf
microseismic events
http://onlinelibrary.wiley.com/doi/10.1029/JB073i012p03945/full
Seismic noise
http://onlinelibrary.wiley.com/doi/10.1029/2007GC001814/pdf