July 24, 2013 – Japanese Earthquakes 27 A.D. to 2012 – 1,985 Years: I downloaded 1,985 earthquakes from NOAA and USGS for Japan and graphed 528 earthquakes, greater than or equal to 7.0 magnitude, by local time of day (see above).
I was particularly interested in Japan, since the country does not have daylight savings time and only one time zone. Therefore, I was able to make an accurate chart of the time for 528 quakes. Below, is a map of major Japanese quakes back to 1923, from MapsOfWorld.com.
One purpose was to analyze statements made by Pliny the Elder or Gaius Plinius Secundus (23-79AD); a Roman officer and author of the Natural History Encyclopedia, published in 78AD. Specifically, Pliny states that earthquakes are: “(1) More frequent by night than in the daytime, (2) Severest in the morning and evening and (3) Are frequent near dawn and in the daytime about Noon.” Pliny is apparently separating frequency (quantity) and severity (strength).
Below, is a time matrix for Japan in terms of the average time for sunrise, noon (Sun overhead), sunset and midnight:
‘(1) Pliny: “More frequent by night than in the daytime.”
I assuming nighttime is the 12 hour period from 6PM to 5AM totaling 231 quakes. Daytime is the 12 hours between 6AM to 5PM totaling 297. In this way, day and night both have 12 hours. Therefore, at least for Japan Pliny is wrong; in that 43.8% of the quakes occurred at night, while 56.2% happened in the day time.
‘(2) Pliny: “Severest in the morning and evening.”
Morning: The period of time between midnight and noon, especially from sunrise to noon. Evening: The period of time at the end of the day, usually from about 6PM to bedtime. I’m going to modify these Google definitions as follows: Morning = Six hours from 6AM to 11AM = 145 quakes (54.9%), Evening = Six hours from 6PM to 11PM = 119 quakes (45.1%). Revised this since Pliny said AND. Therefore morning AND evening totals 264 versus 264 for the other 12 hours, which means it’s an exact tie. Pliny gets a tie for this one, not considering severity.
‘(3) Pliny: “Are frequent near dawn and in the daytime about noon.”
Dawn in Japan is between 4:30AM and 6:52AM; use 4AM to 6AM. About noon; use 11AM to 1PM. Both these categories are three hours long. Dawn = 4AM to 6AM = 57 quakes (average 19 per hours). Noon = 11AM to 1PM = 70 quakes (average 23.3 per hour). Chart average per hour = 22. Dawn and about noon miss the tops of 3PM = 42, 3AM and 8AM = 30, and others. By looking at the chart, you can see that dawn, as defined, is low. About noon is low except for the 33 at 11AM, which is the second highest value on the graph. Pliny doesn’t get a win on this one.
Summary: Score Pliny 1 win and 1 lose and 1 tie. Perhaps the quakes by hour of the day would be different, for different countries. I have a database of 707 earthquakes for Indonesia. That country only has two time zones; so that would make a good exercise to further test the ancient Roman scholars earthquake pronouncements. Note: Indonesia has three time zones. I performed a study on Peru, to be published later.
The Master of Disaster