[CEUS-earthquake-hazards] caution on comparison with China

[Liu, Mian]

Jiankang, 

Thanks for your insightful comments. We wrote a paper earlier this year pondering on the same pattern you mentioned. A copy is attached, in case you haven't seen it. 

Cheers, 

Mian

-----Original Message-----
From: ceus-earthquake-hazards-bounces at geohazards.usgs.gov [mailto:ceus-earthquake-hazards-bounces at geohazards.usgs.gov] On Behalf Of Jiakang Xie
Sent: Tuesday, May 03, 2011 2:51 PM
To: ceus-earthquake-hazards at geohazards.usgs.gov
Cc: jiakang.xid at gmail.com
Subject: [CEUS-earthquake-hazards] caution on comparison with China

Dear all,

This email address the comparison with China. Simply put, predicted
hazard map would be of limited use there.

I read the emails on this listserver with great interest. Although I am
no longer working on NMSZ, I can supply some information about
comparison with China. This is so particularly because my father, Prof.
Yushou Shieh (Yushou Xie) have compiled the Chinese historic quakes of
the 2500+ years of written history (in a joint project between the China
Seismological Bureau and Academy of Social Sciences; see
http://www.earth-prints.org/bitstream/2122/797/1/35Wang.pdf , the last
four references; all in Chinese unfortunately).

First regarding the 1956 Chinese national hazard map, it should have
been made by the late Prof. Lee, Shanbang with the assistances with the
Soviet seismologists, as cited by Julio' email. The intensity scale used
should be the Mercalli scale. But please note that the war with Japan
ended in 1945, the Chinese civil war ended in 1950; and the Korean War
ended in about 1954. The map could not have been based on much geodetic
data and was only a first, but very primitive one for China. Comparison
of that map with one published in the 2000s is not very meaningful .

Second, much of northern China have numerous faults with annual motions
of about 5 mm/yr. This contrasts the NMSZ.

Third, between 1303 and 1937, there were 7 Earthquakes with M~8 occurred
in eastern/central China. For example by some accounts, the 1556 Huaxian
quake near Xian killed about 800,000 people. The 1679 Sanhe quake near
Beijing caused the emperor living in tent outside the palace for months.
To date not a single one of these quakes spatially repeated with
nearly comparable magnitude.

Fourth, the Northern China quakes often cluster in time. Between
1965-1976, four quakes with M>7 occurred (including Haicheng and
Tangshan quakes). Not a single one with M>7 has occurred in northern
China since 1976, and before 1965 in morden time.

Lastly in western China the fault motion are faster and quakes are more
regular. But even there, quakes can be major surprises. Here is a
statement about the 2008 Wenchuan quake in a paper by Shen et al. on
Nature Geoscience: "we estimate that the failure and rupture along
multiple segments takes place approximately once in 4,000 years (Nature
Geosci., 2, 718-724, published on line 27 Sept 2009)." It is not the
fast-moving Longmenshan fault, but a number of nearby (with about 50 km
distance as I recall), slow moving fault ruptured during the Wenchuan
quake!

I am not an expert on seismic hazard map but if after every major quake
occurred the Chinese had to update their map, the map would not have
been so useful because large quakes in central/northern China have not
recurred, thus the predicted hazards would be biased high. It is also
not clear how one could deal with clustering , and significant
quiescence afterwards in north/central China. Even for western China,
large quake may not occur along fast-moving faults.

Jiakang, "Jack" Xie
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