WEATHER PHENOMENA

 

Some seismicity may be affected by weather due to wind, tidal surge and air pressure systems effects of  the continental mass compared with adjoining plate masses. During the tropical storm season in the Northern Hemisphere we keep an eye on tropical storms which may affect seismicity according to our models.  Currently the following tropical storms appear to have potential to affect seismicity in the coming week:

 

TROPICAL STORM 13E

 

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TS    13E      2017-08-19  00:00 UT  14.9N  118.5W  045 kts  SW of western Mexico

 

Tropical Storm 13E formed southwest of Mexico with winds up to 45 kts. It is expected to track to the west over the next four days turning north around August 22 but no landfall is anticipated at this time. No seismic watch is expected associated with this system.

 

TROPICAL STORM HARVEY

 

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TS    HARVEY   2017-08-19  00:00 UT  13.7N   64.1W  040 kts  West of the Windward Islands      

 

Tropical Storm Harvey continued today in the North Atlantic west of the Windward Islands with winds up to 40 kts. It is expected to track to the west over the next five days. Increases in seismicity in the Windward Island, Venezuela and Nicaragua/Honduras are expected as this storm moves through the region.

 

Tropical Disturbances are also located about 900 km east of TS Harvey and off the coast of northeastern Africa. NHC expects these will become tropical cyclones with low probability in the next two days.

TIDAL EFFECTS ON SEISMICITY

 

The full moon will arrive at 18:30 UT on August 21. Longitudes which are sub-solar at the time of full moon are near 97W and 83E and include the Central U.S. Mexico and Central America in the west and India, China, Afghanistan and western Indonesia in the east. These longitude zones are most likely to see significant tidal triggering within about three days of August 21. Other areas may also see tidal triggering at this time, especially where fluids mitigate seismicity and where vertical motions are common. The much-anticipated solar eclipse of August 21 will pass over much of the central U.S. and will be viewed by millions of people at this vacation time of year. The eclipse is the first to be visible over the entire U.S. in 99 years. The full eclipse will be  visible from the Pacific Northwest through Lincoln, Nebraska and into the  southeast of the U.S. Tidal triggering could occur in Washington, Oregon or Northern California with lesser triggering in the central and southeastern U.S. Like the full moon this will reach maximum when over 97 West longitude (83 East) with maximum effects in the regions of Oklahoma and Kansas. The greatest  eclipse will occur over the New Madrid Fault in Missouri and Tennessee. A  moderate earthquake is possible in this area in the period August 18-25. The M 6.7 in the Central Atlantic today would be at the end point of this eclipse path and may have been promoted by high tidal stresses.

 

 

August 19, 2017 is the twenty-seventh day after the beginning of the new  lunar month. Regions most likely to experience tidal triggering  on this day (With associated magnitude ranges; the percent change in seismicity rate over background seismicity rate on this day of the lunar month; statistical z-value and significance level) are:

 

Region Magnitude range %change z-value Significance level

 

New Britain MB>=4.0 23 2.3 0.04

Puerto Rico MB>=4.0 28 3.1 0.01

So. California MB>=3.0 59 2.0 0.05

Hindu Kush MB>=4.0 17 2.4 0.04

Utah MB>=2.0 19 1.9 0.05

Aleutians MB>=4.0 35 2.7 0.03

 

Regions expected to experience reverse triggering (i.e. they are unlikely to experience a significant event at this period of the lunar cycle) are:

 

 

Region Magnitude range %change z-value Significance level