The earthquake, which occurred near Hualien city on February 6th, 2018, caused serious property damage and casualties to the city of Hualien. Up to now, researches of various aspects motivated to analyzing the causes of the earthquake are still in progress. In this study, we focused on source and ground motion characteristics of the 0206 Hualien earthquake by utilizing slip distribution inversion and ground motion simulation techniques. A wavelet-based method was applied for capturing rupture characteristics of this earthquake. The results show that the rupture exhibited two asperities, larger slips concentrated in the shallow-crust region, and the rupture was a bilateral type. We also performed ground motion simulation, using a 3-D finite-difference method, to model realistic synthetics. The synthetic PGV map shows a good agreement with the observation. By applying slip distribution inversion and ground motion simulation techniques, ground motion characteristics at a specific site can be sufficiently modeled, indicating that the techniques can contribute to earthquake engineering applications and seismic hazard assessments.
A deadly earthquake of Magnitude 6.4 (Mw) shook Hualien area in the eve of February 6th, 2018. The earthquake caused damages to infrastructures, toppling of several tall buildings, and ruptures of surfaces. While most of these were proximal to the Milun fault in Hualien city, the damages extended southward to the northern part of the Lingding fault. Field investigation, radar interferometry, and GPS were used to understand the surface ruptures and co-seismic deformations during the earthquake. Based on the results, the northern segment of the Milun fault indicated larger displacements and deformations concentrated more immediately near the fault trace. The principal stress trended NNW-SSE except in the ChiHsinTan area which trended NNE-SSW.
Both radar interferometry and GPS showed that the east of the Milun and Lingding faults were moving north to NNE, and in Meilun tableland, tens of centimeter of co-seismic uplifts were observed. Areas west of these two faults were moving southward and mostly experienced slight uplift.
Our results found that the damages were closely correlated to the near surface faults and fault system.
The devastating 0206 Hualien Earthquake has caused severe damages in downtown Hualien City. Strong motion records showed that an intensity of VII in PGA scattered over a wide range, while an intensity of VII in PGV, due to velocity pulses, were observed around the central and southern portions of Milun Fault. Results of microtremor measurements indicated that the region, suffered from the intensity VII of PGV, showed a natural frequency of 0.8 to 1.2 Hz. The mainshock of the earthquake presented two significant peaks at 1 and 2 sec in period of the horizontal acceleration spectra. The results of this study summarized that the peak at 1 sec seemed to be due to local site effects, whereas the peak at 2 sec was attributed to the fault rupture observed in the fault-normal E-W components. Moreover, the strong soil nonlinearity in this area may be the cause of the greater vertical PGA as compared to the horizontal PGA at near-fault stations.
Subjected to the 0206 Hualien earthquake, more than 10 people lost their lives due to collapsed buildings, mid- and high-rises. Two years ago, of the 2016 Meinong earthquake, more than 100 people were killed due to toppling of mid- to high-rise buildings. The reconnaissance after the Hualien earthquake found that the collapsed mid- to high-rise buildings were constructed before 1999. From the viewpoint of current seismic design codes, seismic detailing (lap splice, spacing of transverse reinforcement, hook) was not satisfied. From seismic records collected by the stations near the disaster sites, some of the response spectra are different from the design ones. Rich content near the period of 1 second was found, conforming to the range of the fundamental vibration period of mid- to high-rise buildings. From this preliminary reconnaissance, deficiency in seismic capacity and exceedance in seismic demand meeting the current seismic design codes are the possible reasons of the collapses of mid- to high-rise buildings.
A major earthquake with magnitude ML 6.0 occurred in Hualien City at 11:50PM on Feb. 6, 2018. According to the report from the Central Weather Bureau (CWB), the epicenter of the mainshock was located about 18.3 km northeast of Hualien County Government building. The focal depth was 10 km. Residents all over Taiwan felt the earthquake. The largest seismic intensity was up to 400gal above at Hualien City and Nan-ao Township. In order to understand the seismic performance of Hualien school buildings subjected to the 0206 Hualien Earthquake, National Center for Research on Earthquake Engineering collected the data of the school buildings after the shaking. Based on the data, 57 buildings in 29 schools were damaged, accounting for 8.6 percent of all school buildings. In other words, many school buildings were safe in the 0206 Hualien Earthquake. The major types of building damage were nonstructural including overturning of cabinets due to lack of quakeproof anchorages, and excessive deformation or falling of light suspension ceilings.
In addition, the paper also discusses the cases of the damaged buildings with the objective of upgrading the retrofitting construction.
The reconnaissance team of bridge engineering division investigated four bridges in Hualien city immediately after the 6.26-magnitude earthquake struck just off the east coast of Taiwan on February 6, 2018. The aerial image capture device and digital photography system were employed to perform the post-earthquake survey on-site. The Hualien Bridge, located at the Provincial Highway No. 11 between the Jian and the Shoufeng Townships, was damaged due to ground movements induced by the rupture of the Lingding Fault that was believed to have run across the bridge. The other bridges, including the Qixingtan Bridge, the Hualien City NO.3 Bridge, and the Shangzhi Bridge, also suffered different levels of damage resulting from the surface rupture of Milun Fault that passed through or was closed to these bridges. The reconnaissance results and data obtained by this survey may serve as useful references for seismic evaluation and retrofit design and disaster-prevention of bridges in the future.
This paper presents the reconnaissance results of liquefaction-induced settlements of the Hualien Harbor and other liquefaction locations in Hualien City. The erupted materials from the sand volcanoes were taken to perform laboratory physical index tests for understanding their characteristics. The caisson wharf of the Hualien Harbor suffered little damage and deformation. However, the backyard of caissons suffered significant settlements due to liquefaction of the backfill composed of large size gravel and sand mixtures. The liquefaction phenomenon is very spare and localized in Hualien City, causing no damage to structures, and revealing that the sedimentary environment of Hualien area is not easy for soil liquefaction to occur. The particle sizes of erupted materials around sand vents were larger than those of western plains associated with this earthquake and the 1999 Chi-Chi earthquake, respectively.
During the 0206 Hualien Earthquake in Taiwan, many infrastructures were damaged to different extents. Although several researchers have studied surface fault ruptures, the interaction between structures and fault ruptures have not been completely investigated. In this study, we perform a 3D distinct element method (PFC 3D) to simulate full-scale ground deformation and structure damage induced by the sinistral strike-slip fault. The free field model with 60 degrees fault dip angle presented the Riedel shear and the negative flower structure with 50 m wide primary deformation zone. Buildings located in the deformation zone would be damaged (e.g., displacement, rotation, and subsidence) to different degrees and the rupture trace would bypass along buildings in view of the distance to the fault tip. The Hualien Bridge intersected the Lingding Fault orthogonally. The 0206 Hualien Earthquake caused a sinistral-displacement about 70 cm between pier #9 and pier #10 and a 10 cm dextral-displacement in deck #13. The numerical model reveals that such situation could be related to the fault offset. Our preliminary results indicate that the 3-D distinct element method shows a potentiality to elucidate the interaction between near-fault co-seismic deformations and infrastructures.
The 14 November 2016 Kaikoura Earthquake was a Mw=7.8 earthquake that occurred on a complex fault rupture process in the South Island of New Zealand, triggered an estimated number of 80,000-100,000 landslides. The No.1 highway was severely damaged by landslides and remained broken for a long period, attributing to huge losses of agriculture, animal husbandry, and tourism. This earthquake featured complex fault rupture, coastal uplift, landslides and landslide dams, and site amplification effect in the Wellington city bay. The reconnaissance team of NCREE investigated the disaster area in April 2017 and collected relevant data. This summary report included the seeing and learning experience based on the reconnaissance, and is intended as a sharing with geotechnical communities and can be compared to relevant experiences of the 0206 Hualien Earthquake.
A 地(Geo-ground) :大地(地形，地質，地表及地下水文，岩石，土壤；從宏觀、巨觀、至微觀)
B 工(Technologies) :大地工程相關「科技」(材料，能源、動力、機械，資訊，生物，等等科技)
C 開(Operations) :大地工程相關「作業」，(廣義：調查、規劃、設計、施工、使用 、維修、監測、災害防治；狹義：施工)
D 物(Structures) :大地工程相關 「構造物」(基礎，隧道，堤，壩，砌石構造物，坡地，擋土工，垃圾掩埋場，等等)