Chi-Chi Earthquake In Central Taiwan Research Articles

Tracing developing deterioration zones in a damaged dam by using elastic wave tomography

In this paper, the concrete gravity dam built 40 years ago was partially damaged by the M=7.3 Chi-Chi Earthquake in central Taiwan in 1999. The elastic wave tomography method was applied to identify the safety conditions of the repaired dam in 2010. The resulting velocity profiles showed that the total structure conditions were accepted as a good to questionable condition. The filled materials and cracks existed in some dam components. Seven years later, the updating tracing investigation revealed that the pervious detrimental zones were spatially extended and associated with time. These testing results were also consistent with the findings from the ground penetrating radar inspection.

An index to describe the earthquake effect on subsequent landslides in Central Taiwan

Chelungpu fault reactivation produced the 1999 Chi-Chi earthquake in Central Taiwan in 1999, triggering many landslides over a broad area. The ground damage caused by the Chi-Chi earthquake still influences successive rainfall-triggered landslides. The landslide distribution triggered by heavy rainfall during typhoon Mindulle in 2004 has a high correlation to the landslide sites triggered by the previous Chi-Chi earthquake. This research calculated and ordered landslide data for both the area and distance from the Chelungpu fault. The rank correlation coefficient for measuring two covarying variables is employed to quantify the degree of correlation between the landslide distribution and the Chelungpu fault. A high rank correlation coefficient value demonstrates a highly correlated relationship between the subsequent landslides in 2004 and previous Chelungpu fault activity in 1999.

Landslide seismic signal recognition and mobility for an earthquake-induced rockslide in Tsaoling, Taiwan

Landslide seismic signal processing and the Newmark's sliding block analysis are used in this research to analyze the initiation time and mobility of the Tsaoling rockslide triggered by the 1999 Chi-Chi Earthquake in Central Taiwan. A new technique, the time–frequency spectrum analysis, is employed to identify the rockslide initiation and landing times from four real time seismic records of strong ground motion stations. The results suggest that higher frequencies ranging from 30 to 70Hz correspond to the rockslide initiation and sliding process, which are opposed to the low signal frequency of earthquake. The landslide began at 32.5s, the sliding block sped up at 37.5s, and impacted on the opposite riverbank at 76s on the seismic time record. The mobile scenario of Tsaoling rockslide induced by Chi-Chi Earthquake is simulated using Newmark's sliding block analysis. The maximum sliding velocity reaches approximately 75.1m/s. Despite being a simple conceptual model, the Newmark's sliding block analysis provides consistent results with the real time seismic signal analysis and details of the rockslide kinematics.

The influence of sediment cover variability on long-term river incision rates: An example from the Peikang River, central Taiwan

[1] This study explores the hypothesis that the relative frequency of rock exposure in the bed of an incising channel can have a first-order impact on the long-term average erosion rate. The 1999 Chi-Chi earthquake in central Taiwan generated thousands of landslides along the middle reach of the Peikang River. Sediment from these landslides produced widespread aggradation, such that much of the river's bed remains shielded from active bedrock incision. We present data that constrain the spatial and temporal variability of sediment cover for the Peikang River. Because the river is undergoing spatially variable Holocene bedrock incision (1–10 mm/yr), it offers a unique natural experiment to test the influence of intermittent sedimentation on long-term incision rates. Published electrical resistivity surveys at seven locations along the river reveal median sediment depth values ranging from 1.9 to 11.5 m. The sediment depth correlates inversely with long-term incision rate and sediment transport capacity. We interpret this as an indication that the frequency of bedrock exposure exerts a major influence on incision along the Peikang River.

How rivers react to large earthquakes: Evidence from central Taiwan

Earthquakes and bedrock river incision are fundamental processes in the evolution of tectonically active landscapes, yet little work has focused on understanding how a bedrock river responds to a single large earthquake. Data from the 1999 M w = 7.6 Chi-Chi earthquake in central Taiwan show dramatic differences in river response that depend on the proximity to the rupture zone. Near the fault scarp, vertical ground deformation intensifi es river incision on a time scale of years to decades, while distal to the fault, landslides induced by the earthquake mantle bedrock on the river bed with sediment, impeding incision for decades to centuries as the material is evacuated. This surprising spatial and temporal variability in bedrock incision caused by earthquakes has implications for the paleoseismic interpretation of bedrock terraces and for the evolution of tectonically active landscapes.

An automatic scheme for baseline correction of strong-motion records in coseismic deformation determination

Coseismic deformation can be determined from strong-motion records of large earthquakes. Iwan et al. (Bull Seismol Soc Am 75:1225–1246, 1985) showed that baseline corrections are often required to obtain reliable coseismic deformation because baseline offsets lead to unrealistic permanent displacements. Boore (Bull Seismol Soc Am 91:1199–1211, 2001) demonstrated that different choices of time points for baseline correction can yield realistically looking displacements, but with variable amplitudes. The baseline correction procedure of Wu and Wu (J Seismol 11:159–170, 2007) improved upon Iwan et al. (Bull Seismol Soc Am 75:1225–1246, 1985) and achieved stable results. However, their time points for baseline correction were chosen by a recursive process with an artificial criterion. In this study, we follow the procedure of Wu and Wu (J Seismol 11:159–170, 2007) but use the ratio of energy distribution in accelerograms as the criterion to determine the time points of baseline correction automatically, thus avoiding the manual choice of time points and speeding up the estimation of coseismic deformation. We use the 1999 Chi-Chi earthquake in central Taiwan and the 2003 Chengkung and 2006 Taitung earthquakes in eastern Taiwan to illustrate this new approach. Comparison between the results from this and previous studies shows that our new procedure is suitable for quick and reliable determination of coseismic deformation from strong-motion records.

Development of shallow seismic landslide potential map based on Newmark’s displacement: the case study of Chi-Chi earthquake, Taiwan

With the development of the geographic information system (GIS), the analysis of regional slope stability under seismic loading has evolved rapidly in recent years. In many studies, the Newmark’s method is used for the computation of displacements triggered by an earthquake on a single slope, while for regional analysis, the infinite slope theory is frequently used due to its simplicity when large amount of computations are required. In this research, the infinite slope theory was examined considering various seismic conditions, material properties, and slope geometry to verify the suitability of the method when applied to regional analysis and development of potential shallow landslide maps. The landslide cases induced by Chi-Chi earthquake in central Taiwan were used in this study for verification. It was found that the infinite slope theory is valid for regional analysis when used with discretion. Based on the calculated Newmark’s displacement and combining the GIS technique, procedures for the potential map development are established in this study.

Vegetation recovery and landscape change assessment at Chiufenershan landslide area caused by Chichi earthquake in central Taiwan

This study discusses vegetation recovery and land cover change with reference to the Chiufenershan landslide, a major disaster caused by the Chichi earthquake, 21 September 1999. Image classification technology, landscape indicators from multi-temporal remotely sensed data and a field survey provide the data. Image differencing methods and threshold values coupled with pre- and post-quake satellite images were used. Multi-temporal images in combination with various vegetation indices were drawn on to classify land cover patterns and discuss differences and suitability of indices. Landscape indicators and field investigations fed into an investigation of vegetation recovery and landscape change. The study results show that the best image classification system is original wavebands coupled with a cropping management factor index (CMFI). The land cover analysis shows that areas of forest and grass are increasing and areas of landslide are decreasing. From the field investigation, because the left and right sides of the landslide area were not disturbed by the earthquake, their calculated similarity index is the highest (30.08%). Miscanthus floridulus is the most dominant pioneer plant at the landslide collapse area with an importance value index (IVI) of 63.6%.

Variability in rainfall threshold for debris flow after the Chi-Chi earthquake in central Taiwan, China

The purpose of this study is to analyze variability in rainfall threshold for debris flow (critical rainfall for debris flow triggering) after the M L 7.3 Chi-Chi earthquake in central Taiwan in 1999. Two study sites with different geological conditions were surveyed in the earthquake area. Streambed surveys were conducted to continuously monitor debris flows between 1999 and 2006. During the 7-year study period, every debris flow event was identified, and the streambed characterized. Results show that the rainfall threshold for debris flow was remarkably lower just after the Chi-Chi Earthquake, but gradually recovered. To date, this rainfall threshold is still lower than the original level prior to the earthquake. This variability in rainfall threshold is closely related to the amount of sediment material in the initiation area of debris flow, which increased rapidly due to landslides resulting from the earthquake. With the increase in sediment material, the rainfall threshold was lowered severely during the first year following the Chi-Chi earthquake. However, heavy rainfalls mobilized the sediment material, causing debris flows and transporting sediment downstream. With the decrease in sediment material, the rainfall threshold recovered gradually over time. Furthermore, debris flows occurred only in the subbasins that had sufficient sediment material to cause significant movement. Hence, these results confirm that the sediment material in the initiation area of debris flow is a crucial component of the rainfall threshold for debris flow.

Non-catastrophic landslides induced by the Mw 7.6 Chi-Chi earthquake in central Taiwan as revealed by PIV analysis

The Chi-Chi earthquake occurred in the western foothills of central Taiwan, which triggered coseismic and catastrophic Chiufengershan dip-slope landslides, Tsaoling rockslides and surface stripping of the Jiujiufeng area. After a few days of the Chi-Chi event, the Hongtsaiping area in central Taiwan was reported to have several meters of slide in a small scale area. The reported landslides are dissimilar to the catastrophic events. To better understand the characteristics of such non-catastrophic and unobvious landslide, we try to characterize in detail the sliding directions, their magnitudes and region of the landslide. We analyzed three orthorectified aerial photographs of the Hongtsaiping area, which were taken in 1998/06/13, 1999/11/18 and 2002/10/26, using the Particle Image Velocimetry (PIV) technique. Through the method we correlated the image pixels of the two aerial photographs in order to derive the displacement vector field. The results of the PIV analysis have helped us not only find the areas where sliding had happened, but also evaluate the azimuth and magnitudes of the sliding event. The PIV analysis in the Hongtsaiping area covers a dimension of about 3228 × 2448 pixels in an area of about 1.2 km 2. Our results show that the maximum horizontal displacement of the landslide is about 24 m towards NW in the study area. This unobvious but wide-coverage landslide may need further investigation in mechanisms combining with available or new geological data.

Effects of strength properties of discontinuities on the unstable lower slope in the Chiu-fen-erh-shan landslide, Taiwan

The Chiu-fen-erh-shan landslide was a huge dip-slope avalanche triggered by the devastating Chi-Chi earthquake in central Taiwan in 1999. Anomalous geomorphic precursors, such as ground subsidence and thrust, which are signs of slope instability, were subsequently observed on the lower slope of the Chiu-fen-erh-shan landslide in November, 2002. Post-failure behavior and affected area of the lower part of the landslide must be investigated to provide adequate countermeasures. This study presents the results of the post-failure behavior simulation of the lower slope of the Chiu-fen-erh-shan landslide using Discontinuous Deformation Analysis (DDA). The simulation results show that the surface rocks in the sliding mass move faster and further than the rocks at great depth. The angle of internal friction is found to have a great influence on the failure process than does the cohesion. The sliding rocks are accumulated in the depression in front of the toe of the landslide except under the conditions of very low internal friction. The depression performs as a buffer zone when the lower slope fails.

Application of SAR interferometry to a large thrust deformation: the 1999Mw= 7.6 Chichi earthquake in central Taiwan

SUMMARY Application of the interferometric method to four ERS2-SAR images acquired before and after the 1999 Chichi earthquake has allowed determination of the coseismic surface displacement in the footwall area of the Chelungpu fault. The interferometric results revealed a relative shortening in the round trip distance between the radar antenna and the ground of the footwall side of Chelungpu fault, during the earthquake. This shortening progressively increased from the west to the east and reaches the maximum amount of approximately 26 cm near the central segment of the Chelungpu fault. Our interferometric results have been precisely examined using a dense GPS network in the investigated area. We mapped the GPS coseismic measurements into the radar line of sight and implemented a forward simulation of SAR interferogram from this synthesized result to control our unwrapping performance. In this study, these two observations are compared with a 3-D dislocation model of the fault. Finally, a deformation analysis based on our interferometric result has indicated that a segment with irregular deformation behaviour can be distinguished in the footwall area of the Chelungpu fault. This segment may result from either the influence of inherited basement faults or the presence of a structural terrace that provide local opportunities for superficial deformation.

Coseismic release of water from mountains: Evidence from the 1999 (Mw = 7.5) Chi-Chi, Taiwan, earthquake

Research Article| September 01, 2004 Coseismic release of water from mountains: Evidence from the 1999 (Mw = 7.5) Chi-Chi, Taiwan, earthquake Chi-yuen Wang; Chi-yuen Wang 1Department of Earth and Planetary Science, University of California, Berkeley, California 94720, USA Search for other works by this author on: GSW Google Scholar Chung-Ho Wang; Chung-Ho Wang 2Institute of Earth Sciences, Academia Sinica, Nankang, Taiwan Search for other works by this author on: GSW Google Scholar Michael Manga Michael Manga 3Department of Earth and Planetary Science, University of California, Berkeley, California 94720, USA Search for other works by this author on: GSW Google Scholar Geology (2004) 32 (9): 769–772. https://doi.org/10.1130/G20753.1 Article history received: 22 Apr 2004 rev-recd: 07 May 2004 accepted: 11 May 2004 first online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Chi-yuen Wang, Chung-Ho Wang, Michael Manga; Coseismic release of water from mountains: Evidence from the 1999 (Mw = 7.5) Chi-Chi, Taiwan, earthquake. Geology 2004;; 32 (9): 769–772. doi: https://doi.org/10.1130/G20753.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Earthquake-induced increases in streamflow, producing ∼0.7 km3 of total excess water, were documented after the 1999 (Mw = 7.5) Chi-Chi earthquake in central Taiwan. Analysis of stream gauge data and well records suggests that the excess water originated in the mountains. We propose that the extensive high-angle fractures formed during the earthquake allow rapid release of water from mountains and that mountains in tectonically active areas may be repeatedly flushed by meteoric water at time intervals comparable to the recurrence time of large earthquakes. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Geological and geomorphological precursors of the Chiu-fen-erh-shan landslide triggered by the Chi-chi earthquake in central Taiwan

Special features were correlated to the geological causes of the Chiu-fen-erh-shan landslide, a gigantic rockslide on a dip slope, induced by the Chi-chi earthquake ( M L=7.3) in central Taiwan in 1999. An aerial photo interpretation and the succeeding geological mapping of the failure were employed in this study. A linear depression, a steep step, and a low drainage density in the landslide area were detected from the aerial photos taken in 1998. The gravitational creep was believed to result in the features of the linear depression and the low drainage density. The steep step represented a buckling feature found in the field. The landslide area is composed of stratified sandstone and shale, with dip angles ranging 20–36°. The slip surface developed along a pre-existing bedding fault that resulted from flexural slip folding. Before the Chi-chi earthquake, the rock on the upslope side buckled and was retained by a thick-bedded sandstone downslope. The earthquake shock seriously damaged the sandstone support and led to the catastrophic landslide. This type of landslide is likely to occur on the moderately dipping slope of stratified rocks that were previously deformed by flexural slip folding.

Distributions of landslides triggered by the Chi-chi Earthquake in Central Taiwan on September 21, 1999

An earthquake (M7. 3) took place in central Taiwan on the early morning of September 21, 1999. This disastrous ground shaking is called the Chi-chi earthquake, with its hypocenter about 10km below land surface. Earthquake-induced landslides were surveyed in order to mitigate secondary hazards. The area studied is about 375, 000 ha, in which landslides were identified by aerial photo interpretation accompanied by SPOT images and field surveys. The color aerial photos used in this study are on the scale of 1/17, 000 and were taken between September 22-26, 1999.More than twenty thousand Chi-chi earthquake-induced landslides have been recognized by aerial photo interpretation. The average landslide density and landslide rate are 0.1 pieces/ha and 4.7%, respectively. Over 90% of the landslides were less than one hectare in average and categorized as shallow landslides and rock falls. Most of the landslides occurred in a region between the Chelungpu active fault to the west and the Lishan fault to the east or in regions with a horizontal peak-ground acceleration (PGA) of more than 300 gal. Of the four geological regions in the area studied, the inner foothill zone had the greatest average landslide rate (11.6%) and the greatest number of landslides (9, 090 landslides).The occurrence of earthquake-induced landslides has a close relation to their geology and distances from the earthquake fault. As to geologic formation and PGA, the Ptk2 (Plio-Pleistocene period) formation has the greatest landslides rate, 20% in a 501-600 gal area, and the Pcl formation (Pliocene period) has a landslide rate, 9.2% in a 401-500 gal area. By dividing into six 5-km-wide belts paralleling the Chelungpu fault, the landslide amount and its rate in the Pcl formation area have the greatest value in the 5-10km belt (about 6, 000 amount) and the 10-15km belt (12.7%), respectively. In the Mkc formation area, the landslide amount and its rate have the greatest value in the 0-5km belt, about 1, 400 amount, 4.7%, respectively, and then generally decrease with an increase of 5km.

Geomorphic evidence for prior earthquakes: Lessons from the 1999 Chichi earthquake in central Taiwan

The September 21, 1999, Mw 7.6 Chichi earthquake destroyed several thousand buildings and caused more than 2000 fatalities in central Taiwan. The earthquake occurred along the Chelungpu fault, a thrust fault on the western flank of the Taiwan fold-and- thrust belt. The surface rupture was more than 90 km long, and vertical displacements ranged from 3 to 8 m. Although pre-existing scarps were identified along the Chelungpu fault, the fault had previously been categorized as a less important active fault, owing to the lack of geochronologic evidence and the failure to recognize fault-related geomorphic features. Identifying geomorphic features at active faults in Taiwan will permit the delineation of future sur- face ruptures and the determination of past magnitudes of past earthquakes, thus contributing to hazard assessment.

Assessment of damage in mountain tunnels due to the Taiwan Chi-Chi Earthquake

Tunnels, being underground structures, have long been assumed to have the ability to sustain earthquakes with little damage. However, investigations of mountain tunnels after the Chi-Chi Earthquake in central Taiwan revealed that many tunnels suffered significant damage to various extents. This work describes the findings of a systematic assessment of damage in the mountain tunnels in Taiwan after the earthquake. It was found that among the 57 tunnels investigated 49 of them were damaged. The damage patterns are summarized based on the characteristics and the distribution of the lining cracks. This systematic investigation, involving geological conditions, design documents, construction and maintenance records of these tunnels, has been conducted to assess the potential factors that may have influence on the various damage patterns and the earthquake loading for tunnels. The results show that the degree of damage is associated with the geological condition and structural arrangement of the tunnel. A tunnel passing through a displaced fault zone will definitely suffer damage. The extent of geological weak zones, distance from the epicenter, and the existence of a slope face are also significant influencing factors. The seismic capacity of the tunnel is influenced by its structural arrangement, type of lining, invert setup, lining reinforcement, and other parameters.

Tectonic Environment of the 1999 Chi-Chi Earthquake in Central Taiwan and its Aftershock Sequence

In the early morning of 21 September, 1999, Taiwan experienced its most powerful inland earthquake (with Richter magnitude 7.3) of the century. The earthquake occurred near the small town of Chi-Chi in central Taiwan, in an area with a low recent background of seismicity although it is surrounded by belts of high seismicity. It caused an extensive surface ruptures totaling about 100 km long and a tremendous number of aftershocks. Using seismological and morphological data, we investigate tectonic environment in central Taiwan and the associated plate structure in the Taiwan region, with emphasis on the cause of the earthquake and its aftershock sequence. Taiwan island is situated on the northwestern corner of the Philippine Sea plate, where its interaction with the Eurasian plate is complicated. The Philippine Sea plate moves northwestward with respect to the Eurasian plate. The former subducts northwestward, in general, along the Ryukyu ward and underthrusts westward in the Taiwan region, with the meridianline of l2l.5°E being the present western boundary of the active subductlng lithosphere. The western boundary is migrating westward, at a rate of about 6 cm/y, along with the northwestward movement of the Philippine Sea Plate. The Philippine Sea plate, like a plow, pushes and uplifts Taiwan island situated on the Asian continental margin, as demonstrated by a seismic wedge to the east of 121°E. In central Taiwan, there exist two obvious linear belts of frequent earthquakes, almost perpendicular and individually trending NW and NE. These linear belts form the boundaries of a triangular area with low background seismicity in front of the seismic wedge, including the Peikang basement high, an uplifted pre-Miocene basement beneath the Western Coastal Plain and its offshore zone. The Chi-Chi earthquake occurred in a subarea of the triangular area near the vertex, con. Fined by the seismic belts and the Peikang basement high. ‘The northwestward movement of the subarea has been impeded by the Peikang basement high, and the associated crustal strain energy may have thus been stored, and then released to trigger the Chi-Chi earthquake, the ruptures and the aftershocks.