Electronic Supplement to
Semiannual Earthquake Periodicity

by Patrick H. McClellan

Table S5. Pre-1850 Mainshocks Included in the Northern-California-Region Sample and their Phases in the Semiannual Cycle

Date Time, GMT (hh:mm:ss.ss)* Latitude (°) Longitude (°) Magnitude Phase Source§
June 1838 99:99:99.9900 37.3000 −122.1500 7.40 0.38 to 0.54 UCERF2
18 January 1840 99:99:99.9900 36.8500 −121.5000 6.50 0.657 UCERF2
10 June 1836 15:30:99.99 36.9000 −121.5000 6.40 0.440 UCERF2
3 July 1841 22:07:99.9900 36.8250 −121.5000 6.00 0.564 UCERF2
29 July 1841 08:15:99.9900 36.8000 −121.4500 5.80 0.700 UCERF2
9 October 1781 99:99:99.9900 37.2000 −122.0000 5.50 0.089 UCERF2
11 October 1800 99:99:99.9900 36.8700 −121.5700 5.50 0.101 UCERF2
21 June 1808 99:99:99.9900 37.8000 −122.6000 5.50 0.497 UCERF2
September 1825 99:99:99.9900 37.1000 −122.3000 5.50 0.88 to 0.04 UCERF2
3 April 1827 99:99:99.9900 37.7500 −122.5000 5.50 0.070 UCERF2

“Northern” and “southern” California regions are delimited at latitude 36.5° N.

* 99 denotes the time unit value is unavailable. For 1825 and 1838 events, day of the month is unknown; hence, phase is given as the range from first to last day of month.

† Magnitude type as given in the source.

‡ Phase is the fraction of the cycle elapsed between bounding equinoxes.

§ Source is the catalog version from which earthquake record was taken (UCERF2, Felzer and Cao, 2008; UCERF3, Felzer, 2013).

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