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The electrical properties of Al2O3/n-InGaAs metal–oxide–semiconductor capacitors (MOSCAPs) with In content of 0.53, 0.7, and 1 (InAs) have been investigated. Results show small capacitance–voltage (C–V) frequency dispersion in accumulation (1.70% to 1.85% per decade) for these MOSCAPs, mostly being assigned to border traps in Al2O3. With higher In content, shorter minority-carrier response time and smaller C–V hysteresis are observed. The reduction of C–V hysteresis might be related to the reduction of Ga-bearing oxides in Al2O3/InGaAs interfaces as indicated by x-ray photoelectron spectroscopy.

The Longitudinal Valley fault in eastern Taiwan is the most important arc–continent collisional boundary fault between the Philippine Sea plate and the Eurasian continent. The 50% amount of collisional deformation partitioned on the fault has considered implications for seismic hazard. Our paleoseismological work on the middle segment (the Juisui fault) of the Longitudinal Valley fault has shown that the fault occurred intensive seismicity of four paleoearthquakes of 1951 AD, P2 event

The 1999 Chichi earthquake ruptured along previously unrecognized traces of the Chelungpu fault, because the traces were covered with thick-bedded fluvial, alluvial, and colluvial deposits. The earthquake created a 95-km-long surface rupture and associated fault-related fold scarps. This study focused on the fault-related fold at two locations, where the fold scarp is characterized with trench excavation and shallow cored boring results. The structural characteristics revealed by the two trench sites are consistent with a trishear fault-propagation fold growth above a blind thrust. Several characteristics of the fold observed in the Holocene deposits show smoothly rounded fold-hinges, unconformities, onlapped structure, and downward steepening of forelimb strata. Results from these structures suggest that the fold grows by progressive limb rotation of growth strata in sequential coseismic growth episodes. The growth strata show several unconformable contacts as indicated by paleosoil horizons developed on event horizons. Based on the syntectonic sedimentary structure, three events are revealed at the Siangong-Temple site and two paleoearthquake events on the Shijia site. Integration with the two trenches and the previous studies suggests the three paleoearthquake events occurred 300–430, 710–800, and 1710–1900 yr B.P. These data on the two trench sites indicate that the average slip rate is 4.2 and 4.5 mm/yr, respectively.

The geomorphic expression of the frontal Western Foothills in central Taiwan is usually defined by a late Holocene scarp that ranges from tens to hundreds of meters in height. This scarp is the product of displacement on a near-surface 20- 30 east-dipping thrust fault, the Chelungpu fault, which ruptured during the Chichi earthquake. The large scarp height may correspond directly to the accumulation of successive surface ruptures. The Chushan site is located on the southern part of this fault where the Chichi earthquake produced a scarp with a 1.7-m vertical offset for the total vertical separation. Based on core-boring estimates, the vertical displace- ment on both sides is 7 m along a 24 east-dipping thrust fault. The results from our paleoseismic analysis indicate that five large paleoearthquake events have caused the large offsets during the past 2 ka. The radiocarbon age constraints of the paleoearth- quakes suggest a clustering of 540-790 cal yr B.P. (E2), 710-950 cal yr B.P. (E3), 1380-1700 cal yr B.P. (E4), 1710-1930 cal yr B.P. (E5), and the 1999 Chichi earth- quake. Events E3 and E4 have not been reported in previous studies and we did not observe event E1 (300-430 cal yr B.P.) at the site. Based on displacement and fault segmentation from the geologic features, we argue that the two new events may have occurred along the northern part of the Chelungpu fault. The vertical slip rate is estimated to be at least 3.9 0.2 mm/yr over the past 2 ka, which is similar to the long-term estimation through a calculation of late Pleistocene-Holocene terrace el- evations on the hanging wall.

We found active faults in the fold and thrust belt between Tunglo town and the Tachia River in northwestern Taiwan. The surface rupture occurred in 1999 and 1935 nearby the study area, but no historical surface rupture is recorded in this area, suggesting that the seismic energyhas been accumulated during the recent time. Deformed fluvial terraces aid in understanding late Quaternary tectonics inthistectonicallyactivearea.ThisareacontainsnewlyidentifiedfaultsthatwegroupastheTungloFaultSystem,whichformedafter the area's oldest fluvial terrace and appears at least 16km long in roughly N–S orientation. Its progressive deformations are all recorded in associated terraces developed during the middle to late Quaternary. In the north, the system consists of two subparallel activefaults,theTungloFaultandTungloEastFault,strikingN–Sandfacingeachotherfromoppositesidesofthenorthwardflowing Hsihu River, whose course may be controlled by interactions of above-mentioned two active faults. The northern part of the Tunglo Fault, to the west of the river, is a reverse fault with upthrown side on the west; conversely the Tunglo East Fault, to the east, is also a reverse fault, but with upthrown side on the east. Both faults are marked by a flexural scarp or eastward tilting of fluvial terraces. Considering a Quaternary syncline lies subparallel to the east of this fault system, the Tunglo Fault might be originated as a bending moment fault and the Tunglo East Fault as a flexural slip fault. However, they have developed as obvious reverse faults, which have progressive deformation under E–W compressive stress field of Taiwan. Farther south, a west-facing high scarp, the Tunglo South Fault, strikes NNE–SSW, oblique to the region's E–W direction of compression. Probably due to the strain partitioning, the Tunglo SouthFaultgeneratesenechelon,elongatedridgesandswalestoaccommodateright-lateralstrike–slipdisplacement.Otherstructures intheareaincludeeastward-strikingportionoftheSanyiFault,whichhasnoevidenceforlateQuaternarysurfaceruptureonthisfault; perhaps slip on this part of Sanyi Fault ceased when the Tunglo Fault System became active.

The 1999 Chi-Chi earthquake was caused by rupture of the Chelungpu fault, one of the most prominent active thrust faults of Taiwan. This largest of Taiwan's historical fault ruptures broke the surface for over 90 km at the western base of the rugged mountain range. A short right-lateral tear extended southwestward from the southern end of the Chelungpu fault, and a complex assemblage of shallow folds and faults ran northeastward from the northern end. Vertical offsets averaged about 2 m along the southern half of the Chelungpu fault and about 4 m along the northern half, and offsets of 5 to 7 m were typical along the northern part of the major thrust. The sinuous nature of the surface trace is consistent with seismographic data that indicate a dip of about 30°. The 1999 rupture draws attention to the fact that this active fault system is highly segmented and that this segmentation influences the characteristics of seismic ruptures. Active faults to the south, north, and west of the Chelungpu fault have distinctly different characteristics. Faults to the south and north broke the surface during earthquakes in 1906 and 1935. The active Changhua fault to the west, a blind thrust similar in length to the Chelungpu, has not ruptured in the historical period and should be considered a prime candidate for generating a future earthquake. Manuscript received 4 October 2000.

The 21 September 1999 Chi-Chi earthquake ( M w 7.6) occurred on east-dipping shallow thrust faults that produced a high-relief surface rupture. Extraordinary surface breaks appeared that could be clearly traced for about 100 km across many counties. These thrust faults, the Chelungpu and Shihkang, are part of an active fold-and-thrust belt related to ongoing recent arc-continent collision. Measurement of slip vectors along the earthquake rupture indicates that the orientation of the maximum shear stress changed from a westward direction (N70-90°W) on the Chelungpu fault to a northwestward direction (N30-40°W) on the Shihkang fault. The stress field underwent a clockwise rotation of about 40° during the Chi-Chi earthquake. Near-rupture vertical displacements in the hanging wall of the Shihkang fault have more cumulative displacement than on the Chelungpu fault, which is consistent with Global Positioning System (GPS) measurements. Maximum vertical offset on the rupture was found to be about 10 m by the surficial rupture and GPS measurements. In addition, analysis of crustal deformation by GPS measurements on the hanging wall defines a coseismic uplift related to a fault ramp structure. Our synthesis of geological and geodetic analyses shows the importance of ramp structures associated with thrust faults for generating large earthquakes and provides a general framework for understanding earthquake in fold-and-thrust belts. Large surficial coseismic uplift and strong asperities appear to be a function of fault ramp geometry. Our analysis also indicates that, in general, ramp structures in fold-and-thrust belts may have a high potential in generating large earthquakes. Manuscript received 14 November 2000.

The 1999 earthquake brought about 80-km-long surface ruptures along the Shihkang, Chelungpu, and Tajienshan Faults, central Taiwan. Several trenches have been excavated across the Chelungpu Fault of the middle segment. The surface ruptures display clear scarps ranging from 0.2 to 4 m high, showing a complex geomorphic pattern due to coseismic faulting and folding. In the study, measurement of the vertical offset or structural relief was taken with reference to the hanging wall beyond the trishear deformation zone. Therefore we suggest that, for the measurement of offset, we should disregard the trishear zone, and that structural relief on the hanging wall should be represented as a real vertical offset. The net slip is then calculated from the structural relief and dip angle of the thrust on a vertical plane along the slip direction. Through the excavation of a pineapple field across the Chelungpu Fault, we are able to provide evidence of at least four earthquake events for the past about 1900 years, including the 1999 earthquake. Furthermore, based on the radiocarbon dates and historical record, the timing of the penultimate event is bracketed to be between 430 and 150 years ago, and the average recurrence interval is less than 700 years. These data indicate that the average slip rate is about 8.7 mm/yr for the past 1900 years.

A low interface trap density (Dit) Al2O3/In0.53Ga0.47As/Si MOS capacitor fabricated on an In0.53Ga0.47As heterostructure layer directly grown on a 300 mm on-axis Si(100) substrate by MOCVD with a very thin buffer layer is demonstrated. Compared with the MOS capacitors fabricated on the In0.53Ga0.47As layer grown on the lattice-matched InP substrate, the Al2O3/In0.53Ga0.47As MOS capacitors fabricated on the Si substrate exhibit excellent capacitance–voltage characteristics with a small frequency dispersion of approximately 2.5%/decade and a low interface trap density Dit close to 5.5 × 1011 cm−2 eV−1. The results indicate the potential of integrating high-mobility InGaAs-based materials on a 300 mm Si wafer for post-CMOS device application in the future.