Gravity Survey of Taiwan.

Yen, Horng Yuan; Yeh, Yung‐Hui; Lin, Chia‐Hua; Chen, Kung Jung; Tsai, Yu‐Hui

doi:10.4294/jpe1952.43.685

Cited by 23 publications

(24 citation statements)

References 9 publications

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“…Fur ther north east of the Peikang base ment high, one would ex pect the mag netic anom aly to de crease, since low-grade meta mor phosed pre-Neo gene sand stone and slate with low mag netic sus cep ti bil ity, are exposed, but in fact, a high-fre quency anom aly pres ents around the mid dle part of the West ern Foot hills and Hsuehshan Range. This some what in con gru ent re sult is also found on the Bouguer anom aly dis tri bu tion of this area (Yen et al 1995). As a re sult of this find ing, the tec tonic im pli ca tions for cen tral Tai wan and its ac tual mech a nism will be in vestigated fur ther us ing seis mic ex per i ments.…”

Section: Mag Netic Anom Aly Mapmentioning

confidence: 67%

Magnetic Survey of Taiwan and Its Preliminary Interpretations

Yen¹,

Chen²,

Hsieh³

et al. 2009

Terr. Atmos. Ocean. Sci.

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AB STRACTTo achieve an im proved over all un der stand ing of the tec ton ics of Tai wan, an is land-wide mag netic sur vey, es pe cially in the mostly in ac ces si ble moun tain ranges, was car ried out from July 2003 to Feb ru ary 2004. In to tal, 6063 mag netic points were sur veyed at an av er age spac ing of 2 km. Af ter data re duc tions, a new mag netic anom aly map of Tai wan was con structed. The map shows the range of mag netic anom a lies mostly dis trib ut ing be tween -400 to 400 nT. Anom a lies in the south ern part of Tai wan are much higher than those in the north whilst anom a lies in the west ern plains area are higher than those of the mountain ranges.High-fre quency mag netic anom a lies, gen er ally more com plex and lo cal ized, are found in west cen tral (south of 24°N) and south west ern Tai wan. Smooth and gen tle mag netic anom a lies lie over a ma jor part of the moun tain ranges, ex cept in the south ern seg ment of the Cen tral Range. Ac cord ing to the am pli tude of mag netic anom a lies and their cov er age, this im plies that a broad ex tru sive ultramafite body could ex ist be neath the south ern segment of the Central Range.

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Section: Mag Netic Anom Aly Mapmentioning

confidence: 67%

Magnetic Survey of Taiwan and Its Preliminary Interpretations

Yen¹,

Chen²,

Hsieh³

et al. 2009

Terr. Atmos. Ocean. Sci.

Self Cite

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“…We use the misfit function in the model space Figure 4. (a) Bouguer gravity anomaly of the study area, after removal of linear regional trends from the data (Yen et al, 1995), overlaid on outlines of major structure units of Taiwan. to guide the genetic algorithm inversion in search of the best models for the crustal density structure in central Taiwan.…”

Section: Genetic Algorithm Inversion and Resultsmentioning

confidence: 99%

“…The published Bouguer gravity anomaly of Taiwan (Yen et al, 1995) is used in the present genetic algorithm inversion. The gravity data were based on more than 600 evenly distributed measurements over the island, with an average distance of 7 km between the stations.…”

Section: Geophysical Constraintsmentioning

confidence: 99%

Three‐dimensional crustal structure in central Taiwan from gravity inversion with a parallel genetic algorithm

et al. 2004

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The genetic algorithm method is combined with the finite‐element method for the first time as an alternative method to invert gravity anomaly data for reconstructing the 3D density structure in the subsurface. The method provides a global search in the model space for all acceptable models. The computational efficiency is significantly improved by storing the coefficient matrix and using it in all forward calculations, then by dividing the region of interest into many subregions and applying parallel processing to the subregions. Central Taiwan, a geologically complex region, is used as an example to demonstrate the utility of the method. A crustal block 120 × 150 km2 in area and 34 km in thickness is represented by a finite‐element model of 76 500 cubic elements, each 2 × 2 × 2 km3 in size. An initial density model is reconstructed from the regional 3D tomographic seismic velocity using an empirical relation between velocity and density. The difference between the calculated and the observed gravity anomaly (i.e., the residual anomaly) shows an elongated minimum of large magnitude that extends along the axis of the Taiwan mountain belt. Among the interpretive models tested, the best model shows a crustal root extending to depths of 50 to 60 km beneath the axis of the Western Central and Eastern Central Ranges with a density contrast of 400 or 500 kg/m3 across the Moho. Both predictions appear to be supported by independent seismological and laboratory evidence.

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“…Land gravity data were collected over 1980 -2004 by several agencies, including Academia Sinica, the Base Survey Battalion and Ministry of Interior (MOI) of Taiwan. The standard errors of land gravity range from 0.04 to 1 mgal (Yen et al 1995;. The shipborne gravity data were collected by international research vessels from 1960s to 1990s, and these gravity data are available at the National Geophysical Data Center (NGDC; http:// www.ngdc.noaa.gov).…”

Section: Gravity Datamentioning

confidence: 99%

Zonal and Meridional Ocean Currents at TOPEX/Poseidon and JASON-1 Crossovers around Taiwan: Error Analysis and Limitation

Hwang¹,

Shih²,

Guo³

et al. 2008

Terr. Atmos. Ocean. Sci.

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A crossover method for determining zonal and meridional ocean current components is examined using data at three crossovers of TOPEX/Poseidon and JASON-1 ground tracks over 2002 -2006. To implement this method, a geoid model around Taiwan is constructed using surface and airborne gravity data. The modeled and observed geoidal heights at coastal benchmarks are consistent to 5 cm RMS with the means removed. The error and limitation of this method are discussed, concluding that, in order to obtain current velocities at a 10 cm s -1 accuracy and a 6-km resolution, the dynamic ocean topography (DOT) at a mmlevel accuracy is needed, which is not possible to achieve today. By filtering DOT to a spatial scale of 100 km or coarser, a 10 cm s -1 accuracy of velocity may be obtained. One crossover (A) is situated south of Taiwan and near the Kuroshio, the second (B) is at the axis of the Kuroshio and the third is located in the northern Taiwan Strait. These three crossovers feature different ocean current patterns. At a spatial scale of 120 km, the agreement among the altimeter, the Princeton Ocean Model (POM), and the drifter-derived velocities is the best at B, followed by that at A, and then C. In fact, at C the altimeter-derived velocities contradict the POM-derived values, and the tide model error is to be blamed. Further improvement on geoid modeling is suggested.

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Gravity Survey of Taiwan.

Cited by 23 publications

References 9 publications

Magnetic Survey of Taiwan and Its Preliminary Interpretations

Magnetic Survey of Taiwan and Its Preliminary Interpretations

Three‐dimensional crustal structure in central Taiwan from gravity inversion with a parallel genetic algorithm

Zonal and Meridional Ocean Currents at TOPEX/Poseidon and JASON-1 Crossovers around Taiwan: Error Analysis and Limitation

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