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The December 31, 1934 earthquake

M6.4near Alberto Oviedo Mota, B.C., MX, Arizona

A magnitude 6.4 earthquake 3.7 miles deep, 30.3 miles off Yuma County. The 3rd strongest in Arizona’s record since 1900, and the strongest within 50 miles since a magnitude 6.6 on November 20, 1915. 7 aftershocks of magnitude 2.5 or more followed within 30 days.

The earthquake

Magnitude
6.4
local magnitude (ml)
Depth
3.7 mi
6.0 km below the surface
Local time
Monday, December 31, 1934
11:45 MST; 18:45 UTC
Epicentre
32.18°N, 115.18°W
30.3 mi from Yuma County
In Arizona’s record
3rd
strongest of 6,972 since 1900
Within 50 miles
2
counties; more on this date

USGS ANSS Comprehensive Earthquake Catalog, event ci3362656 (“5km S of Alberto Oviedo Mota, B.C., MX”). The USGS event page carries the ShakeMap, felt reports and the official summary.

Aftershocks

Earthquakes of magnitude 2.5 or more within 20 miles of the epicentre in the 30 days after.

7

Aftershocks in 30 days

4.0

Largest aftershock, Jan 6, 1935

3

On the first day

5

In the 7 days before

Aftershocks of magnitude 2.5 or more, by day after the earthquake 1: 3 3 2: 0 3: 0 4: 0 5: 1 6: 1 7: 1 8: 1 9: 0 10: 0 11: 0 12: 0 13: 0 14: 0 15: 0 16: 0 17: 0 18: 0 19: 0 20: 0 21: 0 22: 0 23: 0 24: 0 25: 0 26: 0 27: 0 28: 0 29: 0 30: 0 1611162126
  1. The search radius is the surface rupture length expected for an earthquake of this magnitude (Wells and Coppersmith, 1994), at least 20 and at most 600 miles, so a great earthquake's sequence is counted along its whole fault.
  2. Before the modern seismic networks of the 1970s many small aftershocks went unrecorded, so early sequences read short.

Counties and cities within 50 miles

Distance from the epicentre to each county boundary (zero when inside) and to each city centre.

Counties

Cities, largest first

Earthquakes around the epicentre

2,809 earthquakes of magnitude 3 or more within 50 miles of this epicentre since 1973.

Earthquakes of magnitude 3 or more within 50 miles of the epicentre, by year 1973: 16 1974: 19 1975: 30 1976: 68 1977: 34 1978: 42 1979: 50 1980: 40 1981: 4 1982: 5 1983: 12 1984: 14 1985: 14 1986: 36 1987: 45 1988: 36 1989: 38 1990: 18 1991: 26 1992: 15 1993: 48 1994: 16 1995: 10 1996: 9 1997: 23 1998: 25 1999: 58 2000: 35 2001: 27 2002: 86 2003: 16 2004: 22 2005: 31 2006: 60 2007: 20 2008: 108 2009: 83 2010: 1,158 1,158 2011: 96 2012: 68 2013: 42 2014: 16 2015: 19 2016: 15 2017: 14 2018: 13 2019: 12 2020: 15 2021: 21 2022: 8 2023: 19 2024: 43 2025: 11 19731978198319881993199820032008201320182023

Earlier earthquakes of magnitude 5 or more within 50 miles, strongest first

USGS ANSS Comprehensive Earthquake Catalog. Local time is the time zone of the county nearest the epicentre. Magnitudes are as the catalogue reports them.