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:





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TS    28W      2018-09-21  00:00 UT  15.1N  143.4E   45 kts  Mariana Islands


TS 28W formed today in the area north of Guam, Mariana Islands with winds up to 45 kts. It is expected to track to the west reaching areas east of Taiwan as a typhoon around September 26. Moderate to strong enhance of seismicity in Guam and the Mariana Islands has occurred as this storm passed through the region and may continue. The M 5.4 in the Mariana Islands today was probably promoted by stresses from this storm.




September 21, 2018  is the twelfth 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


Australia MB>=4.0 38 3.0 0.01

So Indonesia MB>=4.0 49 3.7 0.01

Global MB>=5.0 5 1.9 0.05


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


Tonga MB>=4.0 -28 -2.0 0.05

Turkey MB>=4.0 -10 -2.0 0.05