The Korean M5.4 earthquake - a research on whether it was caused by geothermal power generating was released

Recently the NHK News On-line reported the following:

韓国 M5.4の地震 地熱発電が誘発か 研究発表

4月29日 4時35分

去年１１月に韓国南部で発生したマグニチュード５．４の地震は、地下に大量の水を高圧で注水する地熱発電によって誘発された可能性が高いとする研究結果がアメリカの科学雑誌に掲載されました。

韓国南部のポハン（浦項）で去年１１月１５日に起きたマグニチュード５．４の地震は、韓国の観測史上２番目の規模で、建物が倒壊するなどして７０人以上がけがをしました。

この地震について、韓国やスイス、イギリスなどの研究グループがアメリカの科学雑誌「サイエンス」に、震源近くの地熱発電が原因ではないかとする研究結果を発表しました。

地熱発電は、地下深くの岩石に高圧の水でひびを入れてそこから出た蒸気を利用して発電しますが、この作業で利用した大量の水が地下にたまって断層に圧力をかけ、地震が誘発された可能性が高いとしています。

研究グループは、観測データを分析し震源の深さと、発電施設の井戸の深さがほぼ一致しているほか、施設の運用開始以降、それまでは観測されることのなかったマグニチュード２以上の地震が複数回起きていると指摘しています。

イギリスの科学誌「ネイチャー」も、この研究結果を紹介する一方で、震源はもっと深かったとする別の研究者の反論や、今後の地熱発電の教訓にすべきだという科学者の意見を伝えています。地熱発電が誘発した地震は過去にもアメリカやスイスで起きていて、今回の地震についても韓国政府が調査を続けています。

Translation

A research result had appeared in an American scientific journal which supposed that the earthquake of magnitude 5.4 which occurred at southern Korea in November last year had a high possibility of being caused by the injection of a large amount of water by high pressure into the underground for generating  geothermal power.

An earthquake of magnitude 5.4 had occurred on November 15 last year at Pohan of southern Korea, it was the 2^nd largest scale in Korean record with buildings collapsed etc. and more than 70 people injured.

About this earthquake, study groups from Korea, Switzerland and United Kingdom etc. announced their research results in an American scientific journal "Science" regarding whether the earthquake was caused by the geothermal power generating near the seismic center.

In geothermal power generating, water was injected with high pressure into the rock crack deep underground to cause steams to come out and from it electricity was generated; but because the large amount of water used in this work had accumulated in the underground and thus added pressure to the fault, there was a  possibility that an earthquake was caused.

The study groups analyzed the observational data; while the depth of the seismic center and the depth of the well in electric generating facilities were identical, they also pointed out that  earthquakes with magnitude greater than 2  had not been observed before but now occurred more than once after the starting of the mission.

A British scientific magazine "Nature" was also a party that explained this research result, it conveyed a message that refuted some other researcher's assumption that the seismic center was even deeper, and advised that  scientists should have learn a lesson in future  geothermal power generating. In the past, earthquakes due to geothermal power generating had also occurred in the United States and Switzerland; the Korean government was also investigating this earthquake.

So scientists in Korea should have learned a lesson from this event.