Electronic Supplement to
Semiannual Earthquake Periodicity

by Patrick H. McClellan

Table S1. M ≥ 6.4 Mainshocks (n = 19) 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§
18 April 1906	13:12:21.00	37.70	−122.50	7.80	0.150	UCERF2
26 March 1872	10:30:99.99	36.70	−118.10	7.60	0.033	UCERF2
3 October 1915	06:52:48.00	40.50	−117.50	7.30	0.051	UCERF2
8 November 1980	10:27:33.2000	41.0000	−124.640	7.30	0.259	UCERF3
21 December 1932	06:10:05.00	38.75	−118.00	7.20	0.495	UCERF2
25 April 1992	18:06:5.1800	40.3353	−124.229	7.15	0.195	UCERF3
16 December 1954	11:07:13.00	39.32	−118.20	7.10	0.464	UCERF2
21 October 1868	15:53:99.99	37.70	−122.10	7.00	0.161	UCERF2
18 October 1989	00:04:15.1900	37.0362	−121.880	6.89	0.138	UCERF3
11 April 1872	19:00:99.99	37.50	−118.50	6.80	0.121	UCERF2
15 April 1898	07:07:99.99	39.20	−123.80	6.70	0.138	UCERF2
19 April 1892	10:50:99.99	38.40	−122.00	6.60	0.163	UCERF2
8 October 1865	20:46:99.99	37.20	−121.90	6.50	0.088	UCERF2
30 September 1894	17:36:99.99	40.30	−124.50	6.50	0.042	UCERF2
21 December 1954	19:56:29.0000	40.7800	−123.870	6.50	0.494	UCERF3
31 March 1898	07:43:99.99	38.20	−122.50	6.40	0.058	UCERF2
23 April 1906	09:10:99.99	41.00	−124.50	6.40	0.176	UCERF2
1 July 1911	22:00:99.99	37.25	−121.75	6.40	0.548	UCERF2
6 June 1932	08:44:22.0000	40.7500	−124.500	6.40	0.416	UCERF3

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

* 99 denotes the time unit value is unavailable.

† 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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