Predicting Earthquakes: The Mw9.0 Tohoku Earthquake and Historical Earthquakes in Northeastern Japan

Abstract

A magnitude 7.3 foreshock occurred two days before the magnitude 9.0 Tohoku Earthquake. The energy release of earthquakes within two days after the M7.3 earthquake is obviously different from the aftershocks of the Mw9.0 earthquake. But guided by historical earthquake experience, seismologists regarded the M7.3 earthquake as the main shock rather than a foreshock of another greater earthquake. Based on the analysis of historical earthquakes in coastal areas of northeastern Japan, the recurrence time of earthquakes is in quasi-periods of decadal or centennial scale. These quasi-periods are related to fault rupture along subduction zones located in marine environments adjacent to the coast. The probabilistic prediction for future earthquakes made by Japanese seismologists using historical earthquake data is based on a decadal scale quasi-period. It is difficult, however, to make relatively reliable predictions about the recurrence interval of rare great earthquakes based on historical earthquakes due to the very long intervals between large magnitude quakes and the limited historical and scientific records about their characteristics.

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© The Author(s) 2012. This article is published with open access at Springerlink.com www.ijdrs.org www.springer.com/13753
Int. J. Disaster Risk Sci. 2012, 3 (3): 155–162
doi:10.1007/s13753-012-0016-0
ARTICLE
* Corresponding author. E-mail: liujifu@bnu.edu.cn
Predicting Earthquakes: The Mw9.0 Tohoku Earthquake and
Historical Earthquakes in Northeastern Japan
Jifu Liu1,* and Yongsheng Zhou2
1State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, China
2State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China
Abstract A magnitude 7.3 foreshock occurred two days
before the magnitude 9.0 Tohoku Earthquake. The energy
release of earthquakes within two days after the M7.3 earth-
quake is obviously different from the aftershocks of the Mw9.0
earthquake. But guided by historical earthquake experience,
seismologists regarded the M7.3 earthquake as the main
shock rather than a foreshock of another greater earthquake.
Based on the analysis of historical earthquakes in coastal
areas of northeastern Japan, the recurrence time of earth-
quakes is in quasi-periods of decadal or centennial scale.
These quasi-periods are related to fault rupture along subduc-
tion zones located in marine environments adjacent to the
coast. The probabilistic prediction for future earthquakes made
by Japanese seismologists using historical earthquake data is
based on a decadal scale quasi-period. It is difficult, however,
to make relatively reliable predictions about the recurrence
interval of rare great earthquakes based on historical earth-
quakes due to the very long intervals between large magni-
tude quakes and the limited historical and scientific records
about their characteristics.
Keywords earthquake prediction, foreshock, historical
earthquake, Japan, Tohoku Earthquake
1 Introduction
Short-range strong earthquake prediction according to a great
quantity of intensive small earthquakes is one of the common
methods employed in earthquake prediction, and the predic-
tion of the Haicheng Earthquake in China is the most success-
ful example (Chen 2009; Xu et al. 1982). But it is difficult to
tell whether an earthquake that has occurred is a foreshock of
another quake or is itself the main event. On the other hand,
due to a lack of foreshocks (Marzocchi and Zechar 2011),
no forecast was issued for the Tangshan and Wenchuan Earth-
quakes, both of which resulted in considerable casualties.
On 11 March 2011, a Mw9.0 earthquake happened in the
northeast of Japan. Before this Mw9.0 earthquake, a M7.3
earthquake occurred on March 9 in the same place. The
M7.3 earthquake did not attract much attention due to its
occurrence under the sea over 130 km away from the shore.
In this location, the M7.3 quake caused neither severe
destruction nor a devastating tsunami, although the quake
belonged in the strong earthquake category in terms of mag-
nitude. By examining this earthquake and the subsequent
earthquake sequence, researchers later concluded that these
earthquakes were actually a foreshock sequence of a greater
earthquake rather than a typical aftershock sequence of the
M7.3 earthquake (He, Zhou, and Ma 2011; Ozawa et al.
2011). Why was the M7.3 earthquake not recognized earlier
as a foreshock? Seismologists attributed this to the lack of a
history of great earthquakes in northeastern Japan. Thus the
prediction of such an earthquake went beyond the cognitive
range of their seismic activities. Similarly, since no such
strong earthquake occurred in the Longmenshan area before
the Wenchuan Earthquake in China in 2008 (Wen et al. 2009),
seismologists took it for granted that there would be no
strong earthquake in the future in the area, and thus paid little
attention to its possible occurrence.
According to historical earthquake catalogues, earthquakes
have occurred periodically. In China, there have been five
active seismic periods since 1895, marked by the occurrence
of large earthquakes (Zhang, Fu, and Gui 2001). Period of
seismic activity is often used to predict the future trend of
earthquakes. Internationally, Geller and colleagues (1997)
and Sykes, Shaw, and Scholz (1999) hold somewhat opposite
views. According to the self-organized critical (SOC)
phenomenon, Geller and colleagues believe that earthquakes
cannot be predicted. But Sykes, Shaw, and Scholz think
that at a certain scale large earthquakes can be predicted.
Predicting the future trend of earthquakes according to the
quasi-period of historical earthquakes clearly involves great
uncertainties. In practice, prediction according to the caus-
ative rules of historical earthquakes is one of the common
methods for predicting middle- and long-term earthquakes
(Wang 2009). But it is unavoidable for such a method to
fail in predicting great earthquakes with an especially long
causative cycle. This article discusses the limitations of
predicating earthquakes based on historical earthquakes by
analyzing the foreshock characteristics and historical record
of earthquakes in eastern Japan.

156 Int. J. Disaster Risk Sci. Vol. 3, No. 3, 2012
2 Foreshock Activities and Aftershock
Characteristics of the Tohoku Earthquake
On 9 March 2011, a M7.3 earthquake occurred in northeast-
ern Japan off the Sanriku coast; it was accompanied by active
aftershocks including a M6.8 event the next day. These events
were located just north of the Pacific Ocean center of the
Tohoku Earthquake, which took place two days later on 11
March 2011 (Figure 1a). Since the M7.3 earthquake was a
significant earthquake event in its own rights, based on their
experience seismologists took it as the principal earthquake.
Because it caused no damage, the M7.3 earthquake received
little attention from the research community, government,
and general public. But the cruel fact was that this earthquake
and the subsequent earthquake sequence associated with it
were actually a foreshock sequence of a larger magnitude
earthquake rather than a typical aftershock sequence to the
M7.3 earthquake (Figure 1b). Figure 1c shows that the energy
had already been in a gradual attenuation situation more than
half a day after the M7.3 earthquake, and the maximum
magnitude of quakes did not surpass M6.0. However, three
earthquakes stronger than M6.0 happened during the more
than three hour period from 18:06 to 21:22 on March 9, which
made the earthquake energy release rate increase rapidly.
From that point on another five earthquakes stronger than
M5.0 took place, although with a somewhat reduced energy
release rate. The tail end of the curve in Figure 1c is the
occurrence time of the Mw9.0 earthquake. Figure 1c shows
that although the energy release rate before the great earth-
quake was lower compared with immediately after the M7.3
quake, it was absolutely not completely calm (He, Zhou, and
Ma 2011).
Figure 1. Foreshock sequence and the main
shock of the Mw9.0 Tohoku Earthquake: Fore-
shocks and main shock distribution (a); Fore-
shock sequence (b); Energy release (c)
Data source: CEA 2011.

Liu and Zhou. Predicting Earthquakes 157
Compared with the foreshocks, there were intensive strong
aftershocks for several days after the Mw9.0 great earthquake
(Figure 2), which were embodied in crowed lines in the
M-T diagram (Figure 1b), while the frequency of strong
aftershocks decreased gradually (Figure 3a). The variation
tendency of the energy release rate is basically degraded
without obvious fluctuation in the foreshock sequence
(Figure 3b).
These earthquake sequences show that the M7.3 earth-
quake was not the principal earthquake, but part of a fore-
shock sequence. Through analyzing sequences of historical
earthquakes and probabilities of future earthquakes predicted
by Japanese seismologists prior to the great earthquake based
on historical earthquakes, this article explains why seismolo-
gists mistook the M7.3 earthquake as a principal earthquake.
The article also discusses the limitations of predicating earth-
quake according to the data provided by foreshocks and the
historical earthquake record.
3 Characteristics of Historical
Earthquake Sequences in Coastal Areas
of Northeastern Japan
The Tohoku Earthquake happened in the sea off the coast of
Sanriku in northeastern Japan, which belongs to the Pacific
seismic and volcanic activity zone (He, Zhou, and Ma 2011).
Northeast Japan is located at the subduction zone of the
Pacific Plate as it approaches the Japanese archipelago, with
the subduction zone forming the Japan Trench (Figure 4).
Figure 2. Foreshocks, main shock, and aftershocks distribution: Spatial distribution of foreshocks, main shock, and after-
shocks (a); Temporal distribution of foreshocks, main shock, and aftershocks (b); M-T Diagram of the M7.3 foreshock and
other foreshocks stronger than M4.4 prior to the Mw9.0 main earthquake (c)
Data source: Helmholtz-Centre Potsdam - German Research Centre for Geosciences (GFZ) 2011.

158 Int. J. Disaster Risk Sci. Vol. 3, No. 3, 2012
Figure 3. Aftershock sequence and energy release of the Mw9.0 Tohoku Earthquake: M-T Diagram of aftershocks stronger
than M4.4 (a); Changes of accumulated earthquake energy after the Mw9.0 Tohoku Earthquake (b)
Data source: Helmholtz-Centre Potsdam - German Research Centre for Geosciences (GFZ) 2011.
Figure 4. Tectonic settings of the Mw9.0 Tohoku Earthquake in northeastern Japan. A, B, C, and D are the historical earth-
quake areas depicted schematically in Figures 5–8. (b) is the detailed map of the rectangular area in (a)
Source: Adapted from He, Zhou, and Ma 2011.
Southeast Japan is located at the subduction zone of the
Phillipine Plate as it sinks under the Japanese archipelago,
which stretches southward from Izu Peninsula to Shikoku
Island. The Nankai Trough of Japan is formed at the boundary
of the subduction zone (Figure 4a). The boundary between
these two subduction zones is called the Sagami Trough and
the Lzu-Ogasawara Trench.
According to the characteristics of historical seismicity,
the eastern coastal area of the Japanese islands can be divided
into four earthquake zones from the north to south, that is, the
Sanriku area and its near seas earthquake zone, Miyagi area
and its adjacent marine earthquake zone, Kanto area and its
offshore earthquake zone, and the Nankai trough earthquake
zone. Based on the spatial and temporal patterns of historical

Liu and Zhou. Predicting Earthquakes 159
earthquakes in these areas, Japanese seismologists make
predictions about the probability of occurrence of future
earthquakes (Okada 2011).
3.1 Historical Earthquakes in the Sanriku Area and Its
Near Seas
The oldest strong earthquake in history in Sanriku happened
in 869, and the next strong earthquake occurred in 1611.
Thereafter, three M8.0 or greater earthquakes with accompa-
nying tsunami happened in 1677, 1896, and 1933 respectivel y
(Figure 5a). So the tectonics in the offshore areas of both
Sanriku and Fukushima provide the necessary conditions for
the occurrence of M8.0 or greater earthquakes. According to
the predictions based on historical earthquakes, the probabil-
ity of occurrence of M8.0 earthquakes in northern and central
Sanriku and its nearby seas is about 0.5–10 percent in the
97 years after 1933. In contrast, the probability of the occur-
rence of M7.7 earthquakes centered offshore from southern
Sanriku is 80–90 percent in the future 105 years (Okada 2011)
(Figure 5a). According to the energy release diagram of his-
torical earthquakes (Figure 5b), this prediction corresponds
with the basic patterns of energy release. The time sequence
and energy release of the last four earthquakes suggest that
the interval between the first two earthquakes (one cluster)
and the last two earthquakes (another cluster) since 1611 is
short, about a few decades, while the interval between the
two clusters is about 200–300 years. This implies that there
may exist two periods for the seismicity in this area: one is
short, about 50–100 years, and the other is long, about 200–
300 years. Both periods are important for understanding the
occurrence of earthquakes in the area.
3.2 Historical Earthquakes of Miyagi and Offshore
Areas
A M8.2 earthquake occurred in 1793 in Miyagi and nearby
seas, and a series of M7.4 and above earthquakes followed
this quake until 1978. The average interval between these
quakes was about 37 years (Figure 6a). When the earthquake
of M7.2 happened in 2005, Japanese seismologists thought
that the energy did not reach the historical earthquake level.
When the M7.3 earthquake broke out on 9 March 2011,
almost all seismologists believed that it was related to the
earthquake in 2005 (Figure 6b). Therefore the experts thought
the energy had been basically released. Based on historical
earthquakes, Japanese seismologists estimated that the
probability of a M7.5 earthquake reoccurring in Miyagi
and offshore was 99 percent. But if Miyagi marine areas are
linked to South Sanriku, M8.0 earthquakes with the same
probability of 99 percent are possible (Okada 2011).
The evaluation and prediction were reasonable from the
perspective of historical earthquakes. The truth, however, was
that the Mw9.0 great earthquake broke out just two days after
the M7.3 earthquake. The Mw9.0 earthquake was not only the
manifestation of the linkage of Miyagi and near seas with
South Sanriku, but it also revealed the linkage of the entire
northeast ocean trench of Japan because these areas formed a
crack of 400 km along the ocean trench (Ozawa et al. 2011).
The energy released in this strong earthquake exceeded the
total energy released from historical earthquakes since 1835
(Figure 6c). This was totally beyond both historical experi-
ence and seismologists’ cognitive scope, since there was no
Mw9.0 earthquake on record in this area (Ozawa et al. 2011).
Evidently, there is a large uncertainty in predicting future
strong earthquakes based solely on historical earthquakes.
It is relatively reliable to predict moderately-strong earth-
quakes with a quasi-period of a decadal scale. But for huge
earthquakes, the quasi-period reaches from centennial to
millennial scale, and seismologists have limited knowledge
of this type of great earthquakes. For example, according to
paleoseismic analysis, the seismic period of the Wenchuan
Earthquake in 2008 is between 2000 and 3000 years (Zhang
et al. 2008; Wen et al. 2008; Ran et al. 2010).
Figure 5. Historical earthquakes and future earthquake
probability of the Sanriku area and its adjacent marine
areas
Data source: CEA 2011.

160 Int. J. Disaster Risk Sci. Vol. 3, No. 3, 2012
Figure 6. Historical earthquakes and the future probability
of earthquakes in the Miyagi area and adjacent ocean areas
Data source: CEA 2011.
3.3 Historical Earthquakes of the Kanto Area and
Offshore Regions
The Kanto area is controlled by both the Pacific Plate and the
Philippine Plate subduction, and the Pacific Plate subducts
beneath the Philippine Plate, forming the Sagami Trough at
the intersection of the Izu-Ogasawara Trench (the boundary
of the Philippine Plate and the Pacific Plate) and the Japan
Trench (Figure 4) (He, Zhou, and Ma 2011; Ozawa et al.
2011). Five M8.0 earthquakes have occurred in the Kanto
area and offshore districts since 1677. Based on the earth-
quake time series and energy release data, the first two and the
last three quakes have a short time interval of about 20–
40 years. The time interval between the two clusters is
200–250 years. Therefore, two activity periods exist in the
earthquakes of this area, which includes a short period of
20–40 years and a long period of 200–250 years (Figure 7).
3.4 Historical Earthquakes of the Tokai Area and the
Nankai Trough
In history, the Tokai earthquake had prominent one-place
repeatability (Imoto, Wiemer, and Matsuzawa 2006). But
since the Suruga Trough is the extension of the Nankai Trough,
it usually slides with faults along the Nankai Trough during
earthquakes, resulting in energy release that is large in
magnitude and spatial scale. Therefore, the magnitude of
these earthquakes was relatively high, averaging around
M8.0. The earliest three recorded earthquakes were in the
year of 684, 887, and 1096 and 1099 (a double earthquake
type) respectively, with an interval of about 200 years
between major quakes. There was no great earthquake in the
Figure 7. Historical earthquake time series of the Kanto
area and offshore regions
Data source: CEA 2011.

Liu and Zhou. Predicting Earthquakes 161
following 400 years until the M8.4 strong earthquake in 1498.
Since this earthquake, five more great earthquakes of about
M8.0 broke out (He, Zhou, and Ma 2011). The two most
recent of these quakes occurred in 1944 and 1946 with a
magnitude of M7.9 and M8.0 respectively. Coming so close
together, these latest two strong quakes belong to the double
earthquake type, and they can be treated as a single event in
terms of energy release. Therefore, the average period of the
5 earthquakes since 1498 is 110 years (Figure 8). From 1946
onward, 65 years have passed. By counting simply using
the 110-year average period, the next Tokai earthquake will
occur in four to five decades. But this deduction lacks any
theoretical basis (He, Zhou, and Ma 2011).
Theoretically, there are several periods in this seismic
sequence, which is irregular in time, with a short period of
around 110 years, a medium period of around 200 years, and
a long period of around 400 years. These periods correspond
with the slip of fault segments. But when checking the fault
slip and rupture segments in each earthquake, close examina-
tion will reveal completely different periods. The latest study,
for example, indicates that the 1854 Tokai earthquake most
probably corresponds to the 1498 earthquake and the double
earthquake in 1096 and 1099 in term of fault slip segment
(He, Zhou, and Ma 2011). So the average recurrence period is
about 400 years. The double earthquake in 1944 and 1946
corresponds to the earthquakes in 1707, 1361, and 887, with
an average time interval of 350 years. Therefore, calculating
from these two periods, a major M8.0 earthquake will strike
the Tokai area 200 years from now.
Therefore, predictions made according to the seismic
quasi-period determined by earthquake time series may prove
erroneous for medium- and long-term earthquakes. Only by
studying the rupture segment clusters of seismic faults of
similar earthquakes can we determine a relatively reliable
earthquake period, thus acquiring valuable seismic activity
prediction for improved disaster preparedness.
4 Discussions
This section discusses some of the limitations encountered
in the prediction of major earthquakes by focusing on the
following two aspects.
4.1 The Limitation of Predicting Major Earthquake
from Foreshocks
Despite the M7.3 foreshock and a series of medium fore-
shocks that happened before the strong Mw9.0 earthquake in
northeastern Japan, correct conclusions were not drawn about
their significance due to the difficulty in recognizing those
quakes as foreshocks rather than main shock and aftershocks
at the time when they occurred. Whether there is a foreshock
before a major earthquake depends on the degree of fault
instability in the earthquake zone. Ma and Wang (2008) dis-
tinguished three types of earthquake instability: (1) a rupture
earthquake induced by rock failure; (2) a stick-slip earthquake
caused by the unstable sliding along a fault; and (3) a mixed
earthquake that results from the combination of a stick-slip
fault and rock failure. Experiments with rocks under high
temperature and high pressure conditions show that the mech-
anisms of the three types of earthquakes are different, and
thus the abnormal precursors such as foreshocks before strong
earthquakes may also differ. In rupture type earthquakes,
strain energy is usually consumed in rock rupture, so the mag-
nitude of the resulting quake is not high despite a significant
number of abnormal precursors that can be observed before
its actual occurrence. The rupture quake can be described as
“much cry, but little done,” which tends to make people over-
estimate the earthquake’s magnitude and results in a false
forecast. The stick-slip earthquake is characterized by the
strain energy focused on the unstable slip movement along
the fault. In stick-slip quakes the magnitude of the event is
often high. Although there are abnormal precursors, they are
not very noticeable and often also appear shortly before the
main quake occurs. Current technology is unable to measure
the precursors, thus leads to a missed report. The mixed earth-
quake embraces rock rupture along the fault, and also involves
Figure 8. Historical earthquake time series of the Tokai and
Nankai Trough areas
Data source: CEA 2011.

162 Int. J. Disaster Risk Sci. Vol. 3, No. 3, 2012
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unstable lateral slip along the fault. The magnitude of mixed
earthquakes is high, there are precursor events such as
foreshocks, and this type of earthquake offers significant
predictive possibilities.
4.2 The Limitation of Predicting Strong Earthquake
According to Historical Earthquakes
The earthquakes of northeastern Japan have a quasi-periodicit y
of both decadal and centennial scales. These earthquakes
are not only regulated by seismic activity at plate boundaries,
but also influenced by inner plate seismic dynamics. The dif-
ference in quasi-period is a consequence of fault segmental
dislocation. Fault friction stick-slip experiments conducted
under experimental conditions discovered that stick-slip
events have multiplied periodicity (Ma and He 2001), which
means that period doubling bifurcation of stress drop is one
of the non-linear dynamic phenomena in the transition
from stable sliding to stick-slip. Historical earthquakes in
Xianshuihe-Anninghe-Zemuhe fault zone in southwestern
China have occurred in prominent clusters in time and space,
while the seismic rupture of historical earthquakes has clear
segmentation. Medium to strong magnitude earthquakes
cause segmental slip of the fault, forming seismic rupture.
Strong earthquakes cause the overall slip of the entire fault
(Wen et al. 2008). This kind of fault rupture segmentation is
always controlled by plate or interaction along inner plate
boundaries. For example, the north Bayan Har block and
east boundary fault slip in western China have a prominent
relation to great earthquake series (Wen et al. 2011).
5 Conclusion
Although there exist many limitations in earthquake predic-
tion, we believe that with advances in research and experi-
ments many earthquakes can be predicted. For rare great
earthquakes, however, as the seismic period is long and
records are few or even absent, it is difficult to make reliable
prediction based solely on historical earthquakes. The work
presented in this article aimed at establishing a new method
for earthquake prediction. But future research is needed to
provide a theoretical basis in support of this method.
Acknowledgments
This research was supported by the State Key Laboratory of
Earth Surface Processes and Resource Ecology of Beijing
Normal University, State Key Laboratory of Earthquake
Dynamics (Grant No. LED2009A01), the Key Project of the
National Natural Science Foundation of China (91024024),
and the 12th Five-Year Science and Technology Support
Program of the Ministry of Science and Technology, China
(2012BAK10B03).
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