HKO Short-period Seismograph Network enhances understanding of local earthquakes

The intense earthquakes that hit Japan and Taiwan in recent months have raised the awareness of Hong Kong people about the safety of touring in these places. The Hong Kong Observatory has posted on its website http://www.weather.gov.hk/gts/equake/eq_safety_e.htm some earthquake safety rules.

"People travelling to seismic active areas should know the dos and don'ts during an earthquake," the Senior Scientific Officer of the Hong Kong Observatory (HKO), Dr W T Wong, said. "When an earthquake occurs, people caught indoors should take cover under any large furniture and stay away from glass or loose hanging objects. Those in open area should keep away from buildings, steep slopes, and utility wires. After an earthquake, people should stay out of severely damaged buildings and report any damage to the authorities".

Japan and Taiwan, situated along the circum-Pacific seismic belt, experience frequent earth tremors. In comparison, Hong Kong is not located in seismic active zones and the chance for an intense earthquake occurring here is rather low. However, to meet the needs of engineering design, the Hong Kong Observatory has paid due attention to monitoring earthquakes in the vicinity of Hong Kong and, in November 1979, established a short-period seismograph network. This month (November) is the 25th anniversary of the short-period seismograph network.

The seismometers used in this seismograph network are sensitive to seismic waves with periods of around one second, and are suitable for detecting nearby earthquakes. The network initially comprised of three seismograph stations located at Yuen Ng Fan, Cheung Chau and Tsim Bei Tsui. Seismic data was transmitted in real-time to the Hong Kong Observatory Headquarters via dedicated data lines for analysis and archival by a microcomputer data processing system designed and constructed in-house. This was one of the earliest applications of microcomputer for automatic acquisition and processing of telemetric data in Hong Kong. In 1997, the Hong Kong Observatory and the Geotechnical Engineering Office worked together to establish additional seismograph stations at Cape D'Aguilar, Lead Mine Pass, Luk Keng, Siu Lam and Keung Shan, making up a total of eight seismograph stations in the network. The new seismometers used were sensitive to seismic waves with periods from 0.03 to 1 second. The precision of epicentre determination was improved to within 10 kilometres and ground motions down to one nanometre could also be detected.

Since 1999, the Hong Kong Observatory and the Centre for Earthquake Engineering Research (CEER) of the Hong Kong University (HKU) have made use of the seismic data obtained from the short-period seismograph network to study the transmission of seismic waves in the vicinity of Hong Kong, with a view to getting a better understanding of seismic risk in the region. Director of CEER of HKU Professor Adrian Chandler said the results of co-operative studies between HKU and HKO would provide information to help engineers to make detailed seismic risk assessments for the buildings in Hong Kong.

The Hong Kong Observatory has a long history of monitoring earthquakes, that goes back to 1921 when the first seismograph was installed at the Hong Kong Observatory Headquarters at Tsim Sha Tsui. At the same time, the Hong Kong Observatory also began to keep a record of locally felt tremors reported by the people of Hong Kong. The seismometer used was of the long-period type, sensitive to seismic waves with periods around 15 seconds and was suitable for detecting distant earthquakes. The seismic signals detected enabled the determination of the epicentres of intense earthquakes when analysed with data obtained by seismographs in other countries. The long-period seismometer now in use at the Hong Kong Observatory Headquarters has been in operation for nearly 50 years, since the International Geophysical Year of 1958.

The Hong Kong Observatory plans to acquire a broadband seismometer next year to replace the existing long-period seismometer. The new seismometer will enable seismic analysis and epicentre determination to be done with higher accuracies, and will also provide more comprehensive seismic information for use by the construction industry. A broadband seismometer responds well to seismic waves with periods from 0.02 to 100 seconds, overcoming the limitations of long-period and short-period seismometers.

From 1979 to 2004, the Hong Kong Observatory has recorded 51 locally felt earth tremors. Among these events, six earthquakes occurred within Hong Kong including one in 1983 at Mai Po, two in 1982 and three in 1995 over the sea east of the Lantau Island. These six earthquakes were very light with magnitudes of one to three on the Richter scale. There were seven other locally felt tremors caused by earthquakes near Heyuan in Guangdong with magnitudes of about four on the Richter scale. Most of the other events were caused by earthquakes more than 200 kilometres from Hong Kong. Among them, 20 occurred more than 500 kilometres from Hong Kong. Details of these events can be found at the Hong Kong Observatory website at http://www.weather.gov.hk/gts/equake/79felt_e.htm

擔桿島海發生3.5級地震
(明報] 09月 14日 星期四 09:00PM


天文台錄得，在本港東南偏南約36公里擔桿島海域，發生黎克特制3.5級地震，本港多處感到震動及搖晃。

廣 告


天文台表示，經初步分析，震央位於香港之東南偏南約36公里(北緯22.0度，東經114.3度]，即擔桿島海域。這次地震的震級為黎克特制3.5級。

天文台表示，在7時53分接獲多名市民的報告，表示感覺到一次震動。天文台的地震儀亦有錄得震動。柴灣、中環、荃灣及離島多處的市民均感到震動，震動維時2至3秒。

根據天文台的資料，由1874年至今，香港錄得V度(五度]或以上的有感地震有6次。在香港歷史上，只有1918年位於香港東北偏東約300公里的汕頭7.3級地震在本港造成輕微損毀，當時一些建築物的牆壁出現裂痕。這次地震是香港錄得最強的一次，估計達修訂麥加利地震烈度VI至VII度(六至七度]。

自1979年至今，香港共錄得51次有感地震，平均每年約2次。當中大部分的烈度都是介乎III至IV度(三至四度]。最小的是II度(二度]，共有5次，而最大的是V至VI度(五至六度]，只有1次。

這些地震的震中位置大部分都在香港境外，如廣東省的河源和陽江、台灣、菲律賓和北部灣等。

自1979年以來，震中位於本港境內的地震有6次：1983年在米埔(1次]，1982年(2次]及1995年(3次在大嶼山東部離岸海域。這些境內地震引起的振動均屬輕微，烈度在V度(五度]以下。

Related thread - Earthquakes in Hong Kong
http://skyscrapercity.com/showthread.php?t=155642

Feeling shake of tonight after dinner although it's not too seriously compared with Asia Region - Japan, Taiwan even Bangkok

Not usual in Hong Kong to be happening :D:

Does anyone who are encounter to of tonight ?

天 文 台 指 今 次 是 04 年 以 來 首 次 有 感 地 震
2006-09-14 HKT 22:36 香港電台網
李俊傑報道

天 文 台 在 晚 上 七 時 五 十 三 分 ， 錄 得 一 次 地 震 ， 強 度 黎 克 特 制 三 點 五 級 ， 震 央 位 於 香 港 東 南 偏 南 的 的 擔 桿 島 海 域 。 天 文 台 高 級 科 學 主 任 黃 永 德 表 示 ， 接 獲 多 宗 市 民 報 告 ， 指 在 多 個 地 區 都 感 受 到 震 動 。

黃 永 德 說 ， 今 次 是 零 四 年 後 ， 第 一 次 有 市 民 感 覺 到 地 震 。 本 港 自 一 九 七 九 年 起 ， 平 均 一 年 有 兩 次 市 民 感 覺 到 的 地 震 紀 錄 ， 大 部 份 震 央 在 台 灣 及 廣 東 省 內 陸 ， 香 港 境 內 過 去 亦 曾 發 生 六 次 ， 包 括 大 嶼 山 同 米 埔 。

Rare earthquake shakes Hong Kong

HONG KONG, Sept 14, 2006 (AFP) - An earthquake rattled Hong Kong Thursday causing skyscrapers to shake and sending people running into the streets in rural areas, officials and witnesses said.

The Hong Kong Observatory said the quake, measuring 3.5 on the Richter scale, struck in the sea around 36 kilometres (22.40 miles) off the coast of Hong Kong, which sits on the southern Chinese coast.

Hong Kong is one of the world's major financial centres and has some of the tallest, most closely-packed high rise buildings in the world.

Police said there were no initial reports of injuries or casualties, but local radio stations were inundated with telephone calls and e-mails as worried residents all over the territory sought information on what happened.

"The floodgates just opened," said DJ Peter King, who was presenting his daily show when the temblor struck.

"Ive not known anything like it -- callers simply wanted to know what was going on. Callers thought it was a plane, a plane crash or even loud building work.

"Most said the same thing -- that their furniture had moved and the house had shaken. I had said on air that there was nothing to worry about as we are not in a quake zone and then the observatory said it had happened just a few miles away," he added.

English teacher Kate Hodgson said residents of the village of Shek O on Hong Kong island ran into the streets after the tremor struck.

"I was lying on my bed reading a book when out of nowhere the walls and furniture started to shake. The whole house moved," she said.

"I didn't know what it was because I had never felt anything like it before," said Hodgson, who picked up her nine-month-old baby Mathilda and left her house.

She said the streets of the village were full of people wondering what had happened.

Martine Montagne, 46, who has lived in Hong Kong for 11 years, said her building in the Tai Tam district shook for around three seconds.

"I've lived in earthquake zones before but I have never experienced anything like this in Hong Kong," she said.

Another Shek O resident said the earthquake was mild compared to what she had experienced back home.

"Everything would come off the wall during an earthquake in Japan, all the walls would be moving around at the same time, everything vibrating. So compared with Japan, this was pretty small," she said.

According to the Hong Kong Observatory website, just six tremors measuring over 5.0 on the Richter Scale have hit the territory since 1874.

From 1979, a total of 51 tremors, measuring up to 4.0 on the Richter Scale, were reported.

The epicentres of most locally felt tremors lie outside Hong Kong, in Guangdong, Taiwan and the Philippines.

Small-intensity earthquake shakes Hong Kong
Caroline Kim and agencies
Friday, September 15, 2006


A small-intensity earthquake rattled Hong Kong Thursday night, causing skyscrapers to shake and sending worried people running into the streets.
The Hong Kong Observatory said it recorded a tremor, measuring 3.5, or minor, on the Richter scale, in waters near Hong Kong, at 7.53pm.

The epicenter was initially determined to be in the sea around Dangan Island, about 36 kilometers south- southeast of the territory.

The State Seismological Bureau in Beijing said the quake struck about 40km off the coast of Hong Kong in the South China Sea.

Police said there were no initial reports of injuries or casualties, but local radio stations were inundated with telephone calls and e-mails.

English teacher Kate Hodgson said residents in Shek O on Hong Kong Island ran into the streets after the tremor struck.

"I was lying on my bed reading a book when out of nowhere the walls and furniture started to shake. The whole house moved," she said.

"I didn't know what it was because I had never felt anything like it before," said Hodgson, who picked up her nine- month-old baby Mathilda and left her house.

She said the streets of the village were full of people wondering what had happened.

Martine Montagne, 46, who has lived in Hong Kong for 11 years, said her building in Tai Tam shook for about three seconds.

"I've lived in earthquake zones before but I've never experienced anything like this in Hong Kong," she said.

Many residents throughout the territory reported buildings and furniture shaking for several seconds.

Wong Wing-tak, senior scientific officer at the observatory, said an earthquake of such a small intensity is very common around the world and there was no cause for alarm.

"The possibility of more tremors afterwards is remote," he said.

According to the observatory, Hong Kong has a very small chance of experiencing major tremors since it is located about 600km from the nearest boundary with the Pacific Plate on the circum- Pacific seismic belt that runs through Japan, Taiwan and the Philippines.

The strongest earthquake felt in Hong Kong was in 1918.

It had a magnitude of 7.3 and was centered at Shantou in Guangdong province, about 300km east-northeast of the territory.

The quake caused minor damages and cracks to buildings in the territory.

According to the observatory Web site, just six tremors measuring more than five on the Richter scale have hit Hong Kong since 1874.

http://www.thestandard.com.hk/images/tiger.gif

Rare earthquake shakes Hong Kong
Friday September 15, 1:02 AM

http://sg.yimg.com/xp/afp/20060915/01/4006402075.jpg

An earthquake has rattled Hong Kong, causing skyscrapers to shake and sending people running into the streets in rural areas.

The Hong Kong Observatory said the quake, measuring 3.5 on the Richter scale, struck in the sea around 36 kilometres (22.40 miles) off the coast of Hong Kong, which sits on the southern Chinese coast.

Hong Kong is one of the world's major financial centres and has some of the tallest, most closely-packed high rise buildings in the world.

Police said there were no initial reports of injuries or casualties, but local radio stations were inundated with telephone calls and e-mails as worried residents all over the territory sought information on what happened.

"The floodgates just opened," said DJ Peter King, who was presenting his daily show when the temblor struck.

"Ive not known anything like it -- callers simply wanted to know what was going on. Callers thought it was a plane, a plane crash or even loud building work.

"Most said the same thing -- that their furniture had moved and the house had shaken. I had said on air that there was nothing to worry about as we are not in a quake zone and then the observatory said it had happened just a few miles away," he added.

English teacher Kate Hodgson said residents of the village of Shek O on Hong Kong island ran into the streets after the tremor struck.

"I was lying on my bed reading a book when out of nowhere the walls and furniture started to shake. The whole house moved," she said.

"I didn't know what it was because I had never felt anything like it before," said Hodgson, who picked up her nine-month-old baby Mathilda and left her house.

She said the streets of the village were full of people wondering what had happened.

Martine Montagne, 46, who has lived in Hong Kong for 11 years, said her building in the Tai Tam district shook for around three seconds.

"I've lived in earthquake zones before but I have never experienced anything like this in Hong Kong," she said.

Another Shek O resident said the earthquake was mild compared to what she had experienced back home.

"Everything would come off the wall during an earthquake in Japan, all the walls would be moving around at the same time, everything vibrating. So compared with Japan, this was pretty small," she said.

According to the Hong Kong Observatory website, just six tremors measuring over 5.0 on the Richter Scale have hit the territory since 1874.

From 1979, a total of 51 tremors, measuring up to 4.0 on the Richter Scale, were reported.

The epicentres of most locally felt tremors lie outside Hong Kong, in Guangdong, Taiwan and the Philippines.

http://sg.yimg.com/i/sg/providers/afp.gif

News of today headline ~~~ Sing Tao Post @ HK

http://i112.photobucket.com/albums/n195/makrut/06-0914-21.jpg

10秒搖晃 牆壁爆裂
3.5級地震驚全城
15/09/2006
太陽報

http://the-sun.orisun.com/tsnmain/20060915/img/0915main.jpg

http://the-sun.orisun.com/channels/news/20060915/img/sn02091516_big.jpg
今次香港的地震中，屯門一幢村屋被震至出現裂痕

http://the-sun.orisun.com/channels/news/20060915/img/sn02091506_big.jpg

http://the-sun.orisun.com/channels/news/20060915/img/a40915_big.jpg

一向「穩如泰山」的香港，昨晚發生罕有的「有感地震」，時間雖僅得十秒，但已引起全城關注。受到香港東南偏南三十六公里擔杆島發生的黎克特制三點五級地震波及，昨晚七時五十三分，大批正在吃晚飯的市民感受到震動，港九新界市民感覺地面甚至椅搖晃，屯門麒麟圍一幢村屋的牆壁更被震至爆裂。天文台在錄得地震後未能即時解答震動原因，令市民更見人心惶惶，幸未導致傷亡及財物損失。

事發於昨晚接近八時，不少留在室內環境的市民均感受到大約十秒的地面震動，甚至眼前物件例如睡床、椅、花卉甚至桌上的飯等也在搖晃。未曾感應過如此強烈有感地震的香港市民對此現象非常奇怪，不少人立即致電天文台詢問卻無法得到答案。直至八時十五分，天文台才首度發出新聞稿，承認天文台的地震儀也錄得震動，但須經分析後才能進一步公布震動的資料。

至晚上八時四十七分天文台正式發出公告，證實各區市民紛紛在七時五十三分，感應到的震動，紀錄分析為一次地震，經初步分析，震中位於北緯廿二度、東經一百一十四點三度，即香港東南偏南約三十六公里的擔杆島海域，是黎克特制三點五級。

天文台長亦感震動
震動搖晃的時間雖僅得十秒，已令全港市民「震撼」，多名居於港島半山、東區、西區、大埔甚至龍珠島的讀者紛致電本報講述地震情景，他們聲稱感到像有重型卡車經過，有長者甚至感到頭暈。屈臣氏集團公共關係總經理倪文玲表示，地震期間部分分店職員感到輕微搖晃，但無貨物從架上墜落。

連居於天文台內的天文台台長林超英也感受到地震，他昨晚接受查詢時表示，已立即趕返辦公室了解情況，他解釋，地震震級稱「黎克特制」，而烈度則稱為「修訂麥加利地震烈度表」。昨晚的地震烈度為第四度，即是懸掛的物件在擺動，猶如大鐵球撞牆般震盪、甚至門窗及碗碟等發出聲響等。

林超英又表示，「上天有路，入地無門」，預測天氣可以放氣球上天，搜集數據計算預測陰晴，但地底活動無法放儀器預測，只能待地震發生後，收集數據做分析，無法預測。

南區近震中較強烈
天文台高級科學主任黃永德博士亦表示，今次地震以南區感覺較強烈，主要是南區較接近震中所致。本港每年平均大約發生兩次輕微地震，由於部分地震是在地殼下面發生，地面未必感覺得到，地震主要在台灣海峽地底出現。由於香港遠離地殼變動帶，因此自開埠以來僅發生六次有感地震，當中五次位於大嶼山，另一次則在米埔。

香港過去發生的地震烈度僅在一至三級，即是「無感覺」，或「室內物件有點點擺動」，對上一次出現四級烈度的狀況已是九九年十月二十二日台中發生地震。

至於震中位置的擔杆列島，島內公安派出所值班人員接受電話訪問時表示，感受到幾下輕微的震動，但島內運作、人民生活、對外交通和通訊均如常，至昨晚深夜十時，沒有收到任何求助、傷亡以及建築物損毀的報告。

廣東省地震局值班人員昨晚接受記者電話訪問時證實，接獲珠海市管轄的擔杆島海域發生地震。值班人員初步收到消息為四點一級，其後修正為三點五至三點六級。

didn't feel a thing :-D

Uh........my village house develops cracks even without earthquakes. Is that guy sure it was caused by the shaking?

Shark scare highlights failings in alert system
Present system to be reviewed after contractors were slow to report find
15 September 2006
South China Morning Post

Leisure officials are to review the shark notification system after admitting they had not been informed for more than a week about two sharks discovered off Shek O Beach by its shark barrier contractor.

Speaking at the beach yesterday, the Leisure and Cultural Services Department's chief leisure manager of aquatic venues, Richard Wong Tat-ming, said there was room for improvement in the present system with the contractor, Universal Nets.

"I admit that there is a need to enhance communication between our department and the contractor. There is room for improving the notification system," Mr Wong said. "We have reminded the contractor to report to us immediately if anything abnormal is spotted during regular net inspections."

During a routine inspection on August 31, Universal Nets workers found two dead silky sharks 80cm to 90cm in length outside the nets at Shek O beach. The species is not dangerous to humans, marine biologist Andy Cornish said.

The contractor, which then disposed of the two sharks, informed the department of the discovery only on Monday and submitted only pictures of them.

A news release about the incident was issued by the department late on Wednesday night in response to inquiries from the media - two days after reporters learned about the incident.

According to Universal Nets' website, it has had a contract with the government to maintain shark nets for five years, and it installed nets at five beaches in 1995. It now maintains nets at eight of the city's 32 beaches. All shark nets are inspected twice a week. The company could not be reached for comment.

Asked why the department did not inform the public after learning about the discovery of the sharks, Mr Wong said: "We have to gain a better understanding of the situation and make sure it is safe for swimmers first."

He said the department had asked the Government Flying Services and marine police to monitor Hong Kong waters for any trace of sharks. "Our lifeguards are also given binoculars to search the water," he said.

The contractor was instructed to check all shark nets this week, and no trace of sharks was found.

Regarding the contractor's "late reporting", Mr Wong said: "The contractor used its own judgment on what it found. We do not have a definite conclusion about that, but we will look into this matter."

Alex Kwok Siu-kit, vice-chairman of the Hong Kong and Kowloon Lifeguards' Union, said the department was being irresponsible and pointed out that swimmers' safety would be at risk if lifeguards were required to look for sharks.

"They should be watching swimmers," he said. "If they are distracted, how can they offer emergency services to save lives?"

I watched this chinese movie
about a family migrant from china to hongkong during the 40-50s........in 1 event it shows an earthquake in HongKong during the 50s burnt down lots of neighbourhoods, is that fiction or real?

If HK had an earthquake in the same level of Tokyo or San Francisco, it would be devastating. I can imagine if you live in the top floor of Highcliff and an earthquake measuring 8 on the richter scale happens :eek:

If HK had an earthquake in the same level of Tokyo or San Francisco, it would be devastating. I can imagine if you live in the top floor of Highcliff and an earthquake measuring 8 on the richter scale happens :eek:

It's just a piece of cake for Japanese.

Slim chance of big quake in HK, says weatherman
17 September 2006
South China Morning Post

Hong Kong Observatory director Lam Chiu-ying said yesterday that the city's chances of being hit by a powerful earthquake or a big tsunami were very low.

Rejecting claims that Hong Kong's buildings could be devastated if a major earthquake struck, he assured the public there was no need to panic.

"When the intensity 7 quake in 1918 happened, some simple clay- brick houses suffered cracks, but the buildings today are obviously more sturdy then those in 1918. Plus, structures like the Tsing Ma Bridge have already taken into account the possibility of earthquakes," he said.

A China Earthquake Administration assessment shows that Hong Kong is at risk of a quake on the modified Mercalli scale (MMS) of intensity 7 once every 475 years. On a scale of 1 to 12, intensity 7 means severe shaking strong enough to cause cracks and non-structural damage to buildings.

Mr Lam agreed the biggest earthquake Hong Kong could experience was one of MMS intensity 7.

"The ability of our buildings to resist typhoon winds means they can also resist shaking. True, winds blow from side to side while earthquakes go up and down but our buildings are very stable and strong," he said.

"Last year when the US was hit by a hurricane all their buildings were wrecked. But after the huge typhoon we had in 1999, everything was fine. Only a few windows were broken. Hong Kong buildings are some of the most stable in the world."

He added that although Hong Kong was mostly surrounded by water, the chances of the city being hit by a tsunami were low.

"We live on lucky ground. There are many geographic obstacles blocking waves. We have to thank the heavens for setting up a variety of complex geographic structures to shelter and protect us," said Mr Lam.

Hong Kong was shaken by a quake measuring 3.5 on the Richter scale on Thursday.

The quake - centred 36km away - lasted several seconds and was felt across the city.

Thank god HK is not at risk of a major earthquake!

Most HK buildings are 'quake-proof'
2 June 2008
South China Morning Post

Most buildings in Hong Kong can withstand any earthquakes that might hit, the government says.

However, a study nearing completion into the effects of earthquakes on the city's structures would be evaluated and any necessary regulation changes made, said Edmond Chan Chu-fai, chief structural engineer at the Buildings Department.

Hong Kong has recorded 164 tremors since 1905, including the May 12 Sichuan earthquake, said Observatory scientific officer Wong Wang-chun.

Most were no more intense than a category V on the Modified Mercalli Scale, or "rather strong".

Tremors of intensity V will be felt outdoors and are expected to occur in the city about once every 15 to 20 years.

The strongest tremor was VI to VII. Earthquakes of intensity VII, equal to magnitude 6 on the Richter scale, can happen roughly every 350 to 400 years.

Hong Kong is 600km away from the Pacific Plate that runs through Japan, Taiwan and the Philippines, the nearest tectonic boundary where seismic activity tends to occur.

The epicentre of the Sichuan earthquake was 1,450km away, the furthest yet to be felt in Hong Kong, according to Observatory data.

Hong Kong and neighbouring Guangdong province are classified as having low to moderate "seismicity", which measures the frequency, intensity and distribution of earthquakes in a given area,

Civil Engineering and Development Department chief geotechnical engineer Pun Wai-keung said there was no record of an earthquake causing a landslide in Hong Kong, and the city's man-made slopes were more at risk from heavy rainfall than from tremors.

If there's an earthquake in the subduction zone off the west coast of Luzon, Manila would become like Banda Aceh on a larger scale. The tsunami would devastate Vietnam, southern Taiwan, and Hainan. The coastal islands would spare the Chinese mainland the worst of the effects.

Slopes to be assessed for earthquake risk
27 December 2008
South China Morning Post

Geologists will next year launch a study to assess the risk of landslides on natural slopes in the event of an earthquake.

Studies of earthquakes elsewhere have indicated that a large quake in Hong Kong would be more likely to cause localised landslips than a large-scale avalanche, but no detailed study has been conducted.

In April, the Civil Engineering and Development Department will launch a pilot "seismic microzonation study" in the northwestern New Territories to assess potential effects of a magnitude 7 earthquake on the stability of natural slopes. The study will take place over three years and cost less than HK$10 million.

Launched a year before a fresh phase of the government's landslip prevention programme is due to begin, it will draw on data from 300 earthquake-induced landslips around the world. A team also went to Sichuan to visit areas hit by the May 12 Wenchuan quake.

"Collapse of rocky slopes there was more serious than that of muddy ones. Also, consolidated slopes proved to be quite resistant to quakes," chief geotechnical engineer Pun Wai-keung said.

The study area covers diverse environments, including sedimentary and igneous rocks and landfill sites.

The risk of a big earthquake striking Hong Kong is much lower than in other parts of China and in neighbouring countries such as Japan. Still, experts have estimated that an earthquake of magnitude 7 could strike the city about once in 400 years.

Previous studies by the department have found that the city's man-made slopes and walls are strong enough to withstand magnitude 7 quakes, and that the slopes are more at risk from heavy rain than earth tremors.

But there has never been a study of the effect on natural terrain or of how the local geology and topography may affect an earthquake's impact.

The Geotechnical Engineering Office of the department, which has been carrying out earthquake studies since 1988, classifies the earthquake risk in Hong Kong and Guangdong as "low to moderate".

Hong Kong's rocky terrain may also reduce the impact of earthquakes. Seismic waves are amplified when they reach loose material such as soil, said Ng Sai-leung, professor of geography at Chinese University.

LCQ8: Earthquake risks and its impact on buildings
Wednesday, June 24, 2009
Government Press Release

Following is a question by the Hon Raymond Ho and a written reply by the Secretary for Development, Mrs Carrie Lam, in the Legislative Council today (June 24):

Question:

It has been reported that a member of the Chinese Academy of Engineering who is an earthquake expert has said that earthquakes of Intensity V to VI on the Modified Mercalli Scale might occur in the coming 10 to 30 years in the Guangdong areas, which are situated in the "middle-to-low intensity" earthquake activity zone. In this connection, will the Government inform this Council:

(a) given that the Buildings Department had appointed a consultant to study and assess the earthquake risks in Hong Kong and its impact on local buildings, whether the relevant report has been completed and whether it will be made public; whether the report includes or will include the relevant comments and assessment results made by mainland earthquake experts regarding the chance of earthquakes occurring in the Guangdong areas adjacent to Hong Kong;

(b) as Hong Kong's schools and disaster emergency relief facilities (e.g. buildings such as fire stations, hospitals and police stations) are all wind-resistant, whether such buildings are at present capable of withstanding earthquakes as well; if so, of the intensity of earthquakes these buildings are able to withstand, and whether their seismic resisting capability is comparatively lower than that of the taller buildings in Hong Kong in general; and

(c) given that the earthquakes which occurred in Wenchuan, Sichuan last year demonstrated the importance for buildings to have seismic resisting capability, whether the Government will consider enhancing the seismic resisting capability of schools and the aforesaid disaster emergency relief facilities, so as to ensure that these buildings can be used as temporary shelters and emergency relief command centres in the event of earthquakes; and of the Government's major considerations, other than financial factors, when it considers whether or not to enhance the seismic resisting capability of these buildings?

Reply:

President,

Intense earthquakes in the world mostly occur along the boundaries of crustal plates. Hong Kong lies within the Eurasian plate but not on the boundary of the plate. The well-known Circum-Pacific seismic belt where major plates meet runs through Japan, Taiwan and the Philippines. Hong Kong is quite far away from this seismic belt, with about 600 kilometres from the nearest point. As such, the possibility of serious earthquakes in Hong Kong caused by collision of crustal plates is relatively low. On the other hand, according to geological structure analysis, the faults in Hong Kong are not active. The geological settings are not conducive to causing strong earthquakes. Earthquakes that occur in Hong Kong and its vicinity can cause tremor that can be felt by ordinary people, but the chance of causing serious damage is relatively low. In fact, since 1905 when the Hong Kong Observatory started recording locally felt earth tremors in the territory, Hong Kong has experienced 163 earth tremors of different intensities without causing any casualties. The strongest tremor ever recorded in Hong Kong was of Intensity VI to VII on the Modified Mercalli Scale (MMS). This locally felt tremor, which occurred in 1918, was caused by an earthquake near Shantou and was more than 300 km away from Hong Kong, and inflicted minor damage on the walls of a few buildings constructed under the prevailing building standards at that time. This has been the only earthquake that has caused damage in Hong Kong since 1905.

The reply to the three-part question is as follows:

(a) The Buildings Department (BD) has commissioned a consultancy study on issues concerning seismic effects with a major objective to assess the earthquake risks in Hong Kong and the effects of earthquakes on local buildings. The study was conducted in accordance with internationally recognised methodologies. It covered analysis of seismic data and records in Hong Kong and neighbouring regions, including a large amount of data on the seismic activities occurred in the Southeast China. It also made reference to the code for seismic design of buildings issued by the relevant departments of the Mainland regarding the need for seismic resistant designs for buildings based on the assessment of intensity of earthquakes in the Hong Kong region. The overall study has reached its final phase. The Administration is carefully consolidating and considering the findings of the study and will consult the stakeholders to map out the way forward.

(b) The consultancy study has found that in general the seismic resisting capability of buildings with fewer storeys is lower than that of buildings with more storeys. Schools and disaster emergency relief facilities (e.g. buildings such as fire stations, hospitals, police stations, etc) have been designed to be wind resistant since the 1930s. The standard of wind resistance has been regularly upgraded to meet the changing needs. Therefore, these buildings possess load-resistant and seismic-resistant capabilities. In case where a severe earthquake occurs in the neighbouring regions causing a tremor of MMS Intensity VII in Hong Kong, these buildings are still basically safe and will suffer no serious damage. This has also been confirmed by the consultancy study commissioned by the BD, that is, most of the buildings in Hong Kong are basically safe in the event of an earthquake that may take place in the territory.

(c) As mentioned in the first part of the reply, in exploring the way forward, the Government will take into account public safety and social needs as the primary considerations in examining whether there is a need to further enhance the seismic resisting capability of schools and disaster emergency relief facilities (e.g. buildings such as fire stations, hospitals, police stations, etc).

New seismograph station enhances earthquake monitoring capability
Thursday, February 18, 2010
Government Press Release

http://gia.info.gov.hk/general/201002/18/P201002180113_photo_1013746.JPG
Senior Scientific Officer of the Hong Kong Observatory, Dr Wong Wing-tak, explains the function of the broadband seismometer in the Po Shan Seismograph Station.

The opening of the Po Shan Seismograph Station today (February 18) will enhance the Hong Kong Observatory's capability in monitoring earthquakes.

The station is located inside a drainage tunnel on Po Shan Road, Mid-Levels, Hong Kong Island, about 300 metres deep in the mountain. Far from city traffic and enjoying stable pressure, temperature and humidity, the site is ideal for a seismograph station.

The Po Shan Seismograph Station is equipped with a broadband seismometer and a strong motion accelerometer. The broadband seismometer is capable of detecting earthquakes thousands of kilometres away. The waveform data recorded is disseminated through the Incorporated Research Institutions of Seismology (IRIS) real-time, enabling earthquake and tsunami monitoring centres worldwide to determine more timely and accurately the parameters of earthquakes in the vicinity of South China Sea.

The seismic data processing system installed at the station can also collect and make use of the data recorded by seismometers around the world to compute earthquake parameters (origin time, location of epicentre, focal depth and magnitude). At the same time, it can derive fault plane solution which, together with computer models, will be useful for estimating the arrival time and height of tsunamis reaching Hong Kong.

The strong motion accelerometer in the station is capable of recording peak ground accelerations in severe earthquakes, which will help evaluate the seismic hazard affecting Hong Kong.

Besides the Po Shan Seismograph Station, the Observatory operates a short-period seismographic network that comprises eight stations for monitoring earthquake activities in the vicinity of Hong Kong. These stations are located at Cape D'Aguilar, Cheung Chau, Keung Shan, Lead Mine Pass, Luk Keng, Siu Lam, Tsim Bei Tsui and Yuen Ng Fan.

后海灣發生黎克特制2.8級地震
【15:19】2010年11月19日

【on.cc 東方互動 專訊】 天文台下午2時42分錄得一次地震。經初步分析，震央位於后海灣附近，即香港天文台西北約35公里（北緯22.5度，東經113.9度），強度為黎克特制2.8級。

Earthquake jolts Hong Kong Open
19 November 2010
AFP

http://the-sun.on.cc/cnt/news/20101120/photo/1120-00407-005b2.jpg

A rare earthquake rattled the Hong Kong Open golf tournament on Friday, jolting some of the world's top players and prompting alarmed residents in the city to call local authorities.

There were no reports of any damage or casualties as a result of the 2.8-magnitude quake, which struck in the middle of the afternoon around 30 kilometres (20 miles) north of Hong Kong, near the Chinese city of Shenzhen.

But the tremor was felt across the former British colony's rugged northern New Territories as many of Europe's top golfers completed a tense second round at the Open.

"I felt it on the 14th tee box and, to be honest, my legs were like jelly over the tee shot. (I've) never felt one of those before," said world number 10 Rory McIlroy, who was in a thrilling chase with England's Ian Poulter for the second-round lead in the 2.5 million dollar tournament.

"I bent over on the 14th tee and wondered what it was," said world number 14 Poulter, the clubhouse leader after the second round. "I was just about to peg my ball up so I did feel a little tremor.

"It just felt tiny. It was a bit strange but it didn't put me off."

The tremor was felt as a short, sharp jolt in many of the buildings dotting Hong Kong Golf Club.

"Quite a number of local residents from various parts of the territory reported to have felt this tremor," the Hong Kong Observatory, the city's meteorological agency, said in a statement.

The quake lasted several seconds, it added.

Hong Kong on average records only one or two locally-felt earthquakes a year, according to the Observatory, although mainland China and Taiwan experience tremors that are both far stronger and more frequent.

The Observatory said that no-one was known to have died as a result of an earthquake in the densely-populated city since its records began.

I could feel it yesterday.........