Taiwan Today

Taiwan makes a new breakthrough in earthquake research.

It is no wonder that Taiwan records more frequent seismic activity than most other places in the world, as the island is compressed between two tectonic plates. As a consequence, along with the development of disaster management and response systems, earthquake studies has become one of the most active fields in Taiwanese academia. According to a recent evaluation of earthquake research published this year in the academic journal Scientometrics, Taiwan ranks as the 11th most productive country or territory in earthquake research in terms of publications in major journals or other outlets contained in the Scientific Citation Index and Social Science Citation Index.

In addition to substantial quantity, Taiwan’s earthquake research has won recognition for its quality from the international scientific community. In fact, a recent breakthrough in the field came from a Taiwanese-led team in July this year, when Science magazine published an article that presents the first direct evidence for a longstanding theory positing a causal relationship between groundwater pressure and earthquake occurrences. The lead writer of the article, Ma Kuo-fong (馬國鳳), is a professor in the Department of Earth Sciences at National Central University (NCU) in northern Taiwan’s Taoyuan County and heads the department’s Earthquake Physics and Seismotectonics Research Group. “Seismologists are often asked if it’s possible to predict earthquakes,” Ma says. “While some rule out [that possibility], some believe that it might be possible one day, but only when the physical nature of earthquakes and their initiation mechanisms are understood.” By “predict,” the professor means being able to determine an adequate estimate of the time, place and scale of a coming quake rather than any connection with events claimed to foretell a temblor such as a person’s ears ringing or unusual animal behavior. “These might be relevant, but can hardly be considered scientific,” notes Ma, who is also an adjunct research fellow in the Institute of Earth Sciences at Academia Sinica, Taiwan’s foremost research institution.

Ma and her team made their discovery from data collected at a site in the slip zone—the areas where layers slide past each other in a quake—of the earthquake measuring 7.6 on the moment magnitude scale that hit central Taiwan on September 21, 1999. Known as the 921 Earthquake, or Jiji Earthquake after the town in central Taiwan at the quake’s epicenter, the temblor claimed more than 2,400 lives, injured more than 10,000 people, destroyed tens of thousands of buildings and resulted in tremendous economic losses. Although the event was one of Taiwan’s worst natural disasters, the 921 Earthquake offered an extraordinary chance for seismologists to increase their fundamental understanding of earthquakes, as the large slip occurred at or relatively near the ground surface. That slip was accessible to borehole drilling and scientists seized the opportunity by initiating the Taiwan Chelungpu-fault Drilling Project (TCDP), a scheme aimed at extracting samples from the fault band. In 2004, the TCDP drilled an approximately 2,000-meter-deep bore into the fault at Beitun District in Taichung City, central Taiwan. That was followed by another bore around 1,300 meters deep. The project is the first, and hitherto only, successful fault penetration in the world, according to Ma.

While the ongoing TCDP re--search is funded by the Cabinet-level National Science Council (NSC), the project includes scientists from Japan, Germany and the United States, countries that also rank among the most active in earthquake research. “Looking into a major earthquake holds the key to understanding this natural phenomenon better and increases scientists’ knowledge,” says Ma, a senior member of the TCDP team.

In November 2006, an array of seven seismometers was installed at one of the TCDP sites, with the instruments placed from 947 to 1,274 meters in depth at intervals of 50 to 60 meters. Among a variety of seismic events, the data from the sensors reveals regular micro-earthquakes that clearly show both primary seismic waves (P waves) and secondary shear waves (S waves), as well as smaller events showing distinct P waves but without identifiable S waves. As S waves can travel only through solids, their absence indicates that the cause of some of the ruptures was not the force of the fault movement—the most common cause of earthquakes—but more likely the force of increased fluid pressure, which can lead to explosions or “isotropic (I-type) events.” “Tectonic plate movement would reach a critical point of stress before a rupture occurred and underground water has been considered a key trigger for that critical point,” Ma explains. “Water pressure can produce great force in an instant within a closed space and could cause an earthquake.”

Ruptures resulting from explosive force instead of shear force have been observed by geologists during their field studies in the fault zone, but the cause had not been identified by seismologists until the finding by Ma’s team. “While the earthquakes are quite small, those little explosions create many cracks that can interconnect to form a long fault and cause a bigger earthquake,” says Ma about her team’s hypothesis. She also points to the possibility of similar seismic effects from artificial sources, such as pumping captured carbon emissions into the ground to control global warming. “Our research results could help with the risk management of underground carbon storage,” she notes.

I-type events were observed in a permeable, fluid-rich zone directly below the impermeable slip zone of the Chelungpu fault. Scientists found the TCDP site ideal for detection of such events as they are more common in geological formations under lower stress. “Because major earthquakes often result in decreased stress, recently ruptured tectonic faults provide an ideal setting to understand the active role of fluids in a low-stress environment,” Ma writes in Science. “Thanks to our geological advantages, we can see those minute events in the fault band,” she notes. “We have the only [confirmed] fault-penetrating observation station in the world. Few stations elsewhere drill at the fault zone because it’s not easy to locate a fault exactly and, if one is found, it might not have slipped.” The TCDP site also bears witness to Taiwan’s drilling competence as demonstrated by the project’s partners, which include the oil exploration unit of CPC Corp., Taiwan, the state-run oil refinery, and Feng Yeu Drilling Co. Ltd., a local business specializing in hot spring and geothermal sites. Ma points out that while the drilling work did not pose too many technical difficulties, retrieving rock core samples from deep in the borehole is a very demanding job that requires a high level of engineering expertise. “Despite the relatively soft structure of the fault band, those core samples must be kept intact for scientific investigation,” the professor says. Moreover, she adds that there are many more aspects to the project “beyond scientific concerns,” such as negotiating with the local community and organizing accommodation for students who joined the project to help monitor the drilling site, work on which continued 24 hours a day for almost one year.

Major Finding

In 2011, Ma’s co-leadership in the fault investigation project won her the annual science prize from the Wu Chien-shiung Education Foundation. Established in 1995 by three overseas Chinese Nobel laureates and Taiwanese laureate Lee Yuan-tseh (李遠哲) to commemorate pioneering nuclear physicist Wu Chien-shiung (吳健雄, 1912–1997), the foundation began issuing awards, which honor outstanding female scientists from Taiwan, in 2008. The tribute to Ma as the 2011 prizewinner highlights her study of a retrieved core from the TCDP, which led to the breakthrough by her team in determining that the thickness of the slip zone is a key parameter in understanding earthquake energy release. The finding was published in a 2006 issue of Nature magazine, thus “raising our country’s status in the international academic circle,” the foundation noted, adding that “the TCDP provides the most precise and direct data to help build a reliable earthquake rupture model and marks a major scientific breakthrough for understanding seismic events and even for earthquake prediction.” At the award ceremony, Ip Wing-huen (葉永烜), an astrophysicist and one of the four vice chancellors of the University System of Taiwan, commended Ma as one of the seismologists who visited the 1999 earthquake site immediately after the disaster occurred and conducted firsthand research under difficult and dangerous circumstances. That fearless spirit at a time of national catastrophe is a model not only for women scientists, but for researchers everywhere, Ip said.

Ma points out that, with an expected lifespan of 10 years, the TCDP facilities can be used for scientific purposes for two to three more years. She suggests that the government provide more flexible funding for such long-term research programs, especially if they involve coordination with the private sector. In the case of the TCDP, the increasing cost of renting local land is an example of the need for such flexibility.

Still, as the head of the NSC’s Earth Science Research Promotion Center from 2007 to 2010, Ma recognizes the government’s efforts in cultivating talented Taiwanese scientists. One program to that effect is the council’s Graduate Students Study Abroad Program, which started in 2002 and sponsors local doctoral candidates undertaking advanced study abroad for six months to a year. This year, together with about 130 other doctoral students, Lin Yen-yu (林彥宇), a student of Ma’s at NCU and a coauthor of the Science article, received funding from the project to study seismology at the California Institute of Technology in the United States. “It’s he who read the crucial P wave and S wave data,” says Ma, who looks forward to more insights from Taiwanese researchers in the world of science in years to come.

Write to Pat Gao at cjkao@mofa.gov.tw