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:





----  -------  ----------  --------  -----  ------  -------  ---------------

TS    CEMPAKA  2021-07-23  00:00 UT  20.0N  107.3E   30 kts  South of Hong Kong, China


TS Cempaka continued today in the area southwest of Taiwan Islands with winds up to 30 kts. It is expected to track to the west making landfall south of Hong Kong around July 20. Regional seismicity in Taiwan and the Ryukyu Islands is likely to be enhanced during the next several days.




----  -------  ----------  --------  -----  ------  -------  ---------------

TYPH  IN-FA    2021-07-23  00:00 UT  24.8N  125.0E   85 kts  East of Taiwan


Typhoon In-Fa continued today northeast of Taiwan with winds up to  85 kts. It is expected to track to the northwest reaching the Central Ryukyu Islands and Taiwan around July 21-22. Some seismic enhance is likely in these areas at that time.




----  -------  ----------  --------  -----  ------  -------  ---------------

TD   NEPARTAK  2021-07-23  00:00 UT  24.0N  148.6E   40 kts  East of Volcano Islands, Japan


TD Nepartak formed today in the region east of the Volcano and Bonin Islands, Japan with winds up to 40 kts. It is expected to track to the northwest reaching an area north of Tokyo, Honshu around July 27. Some enhanced seismicity in this area is likely in the Honshu, Japan area as it makes landfall.





The full moon will arrive on July 24 at 02:37 UT. Longitudes which are at local solar midnight at this time are near 40 West and those at local solar noon near 140 East. These include, in the west, the Atlantic Ocean basin and in the east, the western Pacific subduction zone including Japan and portions of Eastern Indonesia. These areas are currently active and could see a strong earthquake in the next week.



July 23, 2021 is the thirteenth 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



Central America MB>=4.0 10 2.1 0.05

Global MB>=6.0 15 2.5 0.03

Utah MB>=0.0 14 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


Central California MB>=2.0 -8 -2.2 0.05