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Rock Mech. Lab.

Date, Lunar Phase and Time of Giant Earthquakes
might be Specified for Each Subduction Zone

Yoshiaki FUJII and Yuki OZAKI
Rock Mechanics Laboratory, Hokkaido Univ., Sapporo, JAPANBackground and objectives
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Rock Mech. Lab.

Background
Earthquakes tend to occur around daily tidal stress peaks(Cochran et al., 2004, Tanaka, 2010, etc.).

Ultimate goal

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To predict dangerous seasons, lunar phase and time ofgiant earthquake occurrences without complex
calculations on tidal stress or statistical analysis
so that ordinary people can greatly reduce damages by
giant earthquakes by well preparing a few dangerous
hours of a few dangerous lunar phases in dangerous
seasons in a year.

Rock Mech. Lab.

Theoretical increment of P-axis stressof a reverse fault by solid earth tideStress increment shows peaks (peak seasons)around the solstices (June and Dec.) for N60 and N30.
around the equinoxes (Mar. and Sept.) for the equator.

What we present here
Effects of season, lunar phase and time on solid tidal
stressFeature of mainly M W8+ earthquake occurrences during
1900-2011 for each subduction zone.

No significant seasonal difference for N15.

0-0.1
-0.2

00-0.1-0.2

100 200 300
Time (day)

0.2

0.1

N60

0

100 200 300
Time (day)

N30

0.2
Tidal stress (kPa)

0.1

Tidal stress (kPa)30.2
Tidal stress (kPa)

Hokkaido Univ. Japan

Tidal stress (kPa)

0.2

0.1
0-0.1
-0.2

00.1
0-0.1
-0.2

100 200 300
Time (day)

N150

100 200 300
Time (day)On the equator

For N0oS30oE fault at 10 km deep assuming a uniform 3000 kg/m3 density and for 2012. Circular orbits for the sun
and the moon for simplicity.

Hokkaido Univ. Japan

Influences of season, lunar phaseand time on tidal stress
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Local (monthly) peak positions by lunar
phase
They appear

Rock Mech. Lab.

Effect of fault strike5

around spring tides for the peak seasons.
at middle tides for non-peak seasons.

Not significant
Nor dip, friction angle as long as for reverse faulting

Local peaks
0.2-0.2

0100 200 300
Time (day)NS30E0-0.1-0.2

0100 200 300
Time (day)0.1
0-0.1-0.2

0N45E30SE0.1
0-0.1-0.2

100 200 300
Time (day)EW30S

100 200 300
Time (day)N

010203040

N45W30SW

N30
0.1

N60
001020
Lunar phase (day)30

Hokkaido Univ. Japan

Rock Mech. Lab.
7

Noon of equinox at the equator
Noon of summer solstice atnorthern mid-high latitudes

0-0.1

Time (day)N60 examples
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0.1

-0.2
0

Tidal stress (kPa)

-0.1

0.1

Tidal stress (kPa)00.20.2
Tidal stress (kPa)

0.1

0.2
Tidal stress (kPa)

0.2
Tidal stress (kPa)

Tidal stress (kPa)

0.2

6

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Latitude
ExamplesSeasonMoon phase
Northern
Alaska, Kuril, Japan Late June
New or full
mid-high lat.
Late Dec.
New or fullNorthern low lat.
Any season
New or full
Equator
New Guinea
Late Mar. and Sep. New or fullIndonesia
Southern low lat. Peru, Tonga
Any season
New or fullSouthernChile
Late June
New or full
mid-high latitude
Late Dec.
New or fullTime
NoonMidnight
Noon or midnight
Noon or midnightIf giant earthquakes occur under thelargest tidal stress increment...

Noon of summer solstice atsouthern mid-high latitudes

NNN
Midnight of winter solstice atsouthern mid-high latitudes.

Midnight of winter solstice atnorthern mid-high latitudes

Noon or midnightMidnight
NoonMidnight of equinox at the equator

Hokkaido Univ. Japan

Hokkaido Univ. Japan

11

Hokkaido Univ. Japan

10

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Basic explanations on tidal force with the layout of Sun, Moon and Earth

0100 200 300
Time (day)N60 example

090(degree)

Lunar phase (day)-90180A spring tide A neap tide

Spring tides

3010High tide and ebb tide usually do not coincide withpeaks of solid tidal force.

Peak seasons

-0.1
-0.2

Rock Mech. Lab.

Off-peak seasons

0

20

0-180

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0.1

0.2

= 0 or 180o

20

Neap tides

100Tidal stress (kPa)

Tidal stress (kPa)High tide and ebb tide may bedifferent from peaks of tidal
force from 30moon.
Lunar phase (day)Rock Mech. Lab.
0.20100

Point of interest

200Date

300

0.1
0-0.1
= 90 or 270o

EarthEarthSun

Moon-0.2Moon

Hokkaido Univ. Japan

010Time (day)1320

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Observations in northern mid-high lat.

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Six of the eight
events concentrated
during Sept.-Nov.

Alaska (N51-N61)

N60 example

Four of them occurred
around spring tides.
No moon position
dependency

090(degree)

0100

200Date100200300

Time (day)2010-90090(degree)

20100180

0100200
Date300

17300

Five of the six events occurred in the peakseasons.
Four of them occurred around neap tide.
Moon located opposite side for four of thesix events.
The large Sumatra events occurred during
lunar phase of 13.9-19.8 days except forthe 2007 event.
2012 Sumatra1

300

8.582007

20020122012

102030
Lunar phase (day)Hokkaido Univ. Japan

10100200
Date

Lunar phase (day)

200

2005

Tidal stress (kPa)

0.2
0.1
0-0.1-0.2

2012 Sumatra 1 & 230102004 Sumatra
2007 Sumatra-90100 200 300Time (day)Equator example

2012 Sumatra2

200-1800

2005 Sumatra

309100Rock Mech. Lab.

090(degree)

180

Lunar phase (day)-0.1

Lunar phase (day)0Hokkaido Univ. Japan

109.5

0-0.2

300-180

2004

0180

300

0-0.1

30

20018030090(degree)

200

Indonesia (N3-S11)

0Time (day)Lunar phase (day)

-90

MW

Tidal stress (kPa)

0.1

30-90

100

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0.2

Equator example -0.20

Hokkaido Univ. Japan

0N30 example

0.1

15

New Guinea (N6-S8)

0-180

Lunar phase (day)Lunar phase (day)10Rock Mech. Lab.

10-0.130

20

Observations around the Equator

200Time (day)Hokkaido Univ. JapanNo season dependency.
Five of seven events occurred
around spring tides.
No moon position dependency canbe observed.

Six of them occurred
lunar phase between
23 and 29 days.
Five of the eightoccurred around=0 or 180o.

0.1-0.2

300-180

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Tidal stress (kPa)

0.2

The peak values of stressincrement is smallest in
this period.

0.2

Six of the eight eventsoccurred in the peakseasons.

Lunar phase (day)Five of the six
earthquakes occurred
during Feb. 4 to May 7.

Rock Mech. Lab.

Kuril (N43-N47)

Lunar phase (day)Stop unreasonable CO2 reduction!

14Tidal stress (kPa)

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20
2005 Sumatra

2004 Sumatra

100

2007 Sumatra

0100

200
Date

300

22300

21

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Peru (S10-S16)
No clear seasonal
dependency is observed.
Tidal stress (kPa)N15 example

0-0.1-0.2

30

0100

10200300

Time (day)30

200-180

20
100

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income, PhD required)?
-90090(degree)

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0.1

Lunar phase (day)Six of them occurred
around spring tides.
No clear moon position
dependency is observed.

Lunar phase (day)Observations in southern low lat.

0.2This agrees with the noseasonal dependency in thetheoretical tidal stressincrement.

180

0100

200
Date

300

23Stop unreasonable CO2 reduction!

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Observations in southern mid lat.

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Chile (S23-S38)

Tonga (S15-S23)

N30 example

0.1
0-0.1-0.2

0100200300

Time (day)30
Lunar phase (day)Lunar phase (day)30
20
100-180-90090(degree)

Hokkaido Univ. Japan

20

1800100200
Date

0.1
0-0.1-0.2

N30 example

0100200300

Time (day)
30

30
20
100-180

1000.2

Lunar phase (day)Tidal stress (kPa)

0.2

Four of the fiveearthquakes occurred in thepeak season.

Four of them occurred atneap tide.
Three of them occurred
around= 0 (beneaththe moon) or 180o.

Seasonal dependency isnot clear.
Six of the seven eventsoccurred around springtides.
No clear moon position
dependency.

Tidal stress (kPa)

Four of the five events
concentrated during Apr.
to June.

Rock Mech. Lab.

Lunar phase (day)Stop unreasonable CO2 reduction!

-90

090(degree)

20
100

180

0100

200
Date

300

Hokkaido Univ. Japan

300

2524

Observations in Japan

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2011 Tohoku (5:46, N38E142) occurredat middel-neap tide (lunar phase: 6.8 day)why not spring tide?

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Japan (N28-N43)

EarthFour of the six
earthquakes occurred
during Mar. 2 to June 15.

Sun

N30 example

Tidal stress (kPa)

They occurred lunar
phase between 4.9-6.3
and 17.9-21.2 days.

Moon

0.1
Fault

0-0.2

Lunar phase (day)30

202011 Tohoku
100-180-90

090(degree)

Tidal stress from sun

2011 Tohoku

-0.1

30
Lunar phase (day)Middle to neap tide!

Stress decrease by ebb tide

0100

200

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300

Time (day)Hokkaido Univ. Japan

20From JMA Web Site

Sea bottomRock Mech. Lab.
Sea level

Tidal stress from moon

192011 Tohoku
1001800100200
Date

9 of the 18 MJMA7+ earthquakes between 20022011 in Japan occurred 1-3 hours after ebb tides.

300

Hokkaido Univ. Japan

Half of the events in just 2 hours!
Number of earthquake (M7+)

18

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Tohoku 2011

0.2

Four events occurred in
the peak seasons.

Only three of themoccurred around=0or 180o.

around the peak of solid tidal stress
84 min after the estimated ebb tide peak based on the ebbtide at the nearest tidal station (Ayukawa, N38E141) at 4:22.

Rock Mech. Lab.

420-6 -4 -2 0 2 4 6
Delay from ebb tide (hr)20Concluding remarks

Findings
Theoretical seasonal dependency of tidal stressincrement

6 Tohoku 2011

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Future studies

significant varies with latitude.
doesn't show significant influences by strike, dip or friction
angle.

Not only solid tidal force but also actual sea level should be ofcourse considered although it will not change timings of springand neap tides.

Occurrences of giant earthquakes shows different
characteristics for each subduction zone.

Minimum detailed analyses on slip direction will be required.

Some of them can be explained by solid tidal stress.
Some of them can't be explained.

Integration of forces acting to the tectonic plates across thesource fault rather than using tidal stress at hypocenter
Or, the balance of the whole tectonic plates on the earth?

Most Japanese MW8+ events occurred under middle toneap tide.
Half of Japanese MJMA7+ events during 2002-2011 occurred
1-3 hours after ebb tides.

Hokkaido Univ. Japan

27

Example of earthquakes at
Aleutian trench, based on animage from Wikipedia
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Japan

Hokkaido Univ. Japantabe noMay int!
opinp
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