ESTIMATION-OF-THE-LOCAL-RESPONSE-USING-THE-NAKAMU_软件设计/软件工程下载-pudn.com

<html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta charset="utf-8"> <meta name="generator" content="pdf2htmlEX"> <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1"> <link rel="stylesheet" href="https://static.pudn.com/base/css/base.min.css"> <link rel="stylesheet" href="https://static.pudn.com/base/css/fancy.min.css"> <link rel="stylesheet" href="https://static.pudn.com/prod/directory_preview_static/622bb43215da9b288bb860be/raw.css"> <script src="https://static.pudn.com/base/js/compatibility.min.js"></script> <script src="https://static.pudn.com/base/js/pdf2htmlEX.min.js"></script> <script> try{ pdf2htmlEX.defaultViewer = new pdf2htmlEX.Viewer({}); }catch(e){} </script> <title></title> </head> <body> <div id="sidebar" style="display: none"> <div id="outline"> </div> </div> <div id="pf1" class="pf w0 h0" data-page-no="1"><div class="pc pc1 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/622bb43215da9b288bb860be/bg1.jpg"><div class="t m0 x1 h2 y1 ff1 fs0 fc0 sc0 ls0 ws0">Romanian Reports in Physics, Vol. 60, No. 1, P. 131–144, 2008</div><div class="t m0 x2 h3 y2 ff2 fs1 fc0 sc0 ls0 ws0">ESTIMATION OF THE LOCAL RESPONSE USING</div><div class="t m0 x1 h3 y3 ff2 fs1 fc0 sc0 ls0 ws0">THE NAKAMURA METHOD FOR THE BUCHAREST AREA</div><div class="t m0 x3 h4 y4 ff3 fs2 fc0 sc0 ls0 ws0"></div><div class="t m0 x4 h5 y5 ff2 fs0 fc0 sc0 ls0 ws0">BOGDAN ZAHARIA, MIRCEA RADULIAN, MIHAELA POPA, BOGDAN GRECU,</div><div class="t m0 x5 h5 y6 ff2 fs0 fc0 sc0 ls0 ws0">ANDREI BALA, DRAGOS TATARU</div><div class="t m0 x6 h2 y7 ff1 fs0 fc0 sc0 ls0 ws0">National Institute for Earth Physics, 12 Calugareni St., 077125, P.O. Box MG<span class="_ _0"></span>-2 Magurele, Romania,</div><div class="t m0 x7 h2 y8 ff1 fs0 fc0 sc0 ls0 ws0">Tel.: +4021 493 01 17, Fax: +4021 493 00 53</div><div class="t m0 x8 h5 y9 ff2 fs0 fc0 sc0 ls0 ws0">(Received September 20, 2006)</div><div class="t m0 x9 h5 ya ff1 fs0 fc0 sc0 ls1 ws0">Abstract.<span class="_ _1"> </span><span class="ff2 ls2 ws1">Bucharest is one of the most affected cities by earthquakes in Europe. Situated <span class="_ _2"></span>at</span></div><div class="t m0 x1 h5 yb ff2 fs0 fc0 sc0 ls3 ws2">150–170 km distance from the Vrancea epicentral zone, Bucharest has suffered <span class="_ _2"></span>many damages due to</div><div class="t m0 x1 h5 yc ff2 fs0 fc0 sc0 ls2 ws3">high energy Vrancea intermediate-depth earthquakes. For example, the 4 March 1977 event produced</div><div class="t m0 x1 h5 yd ff2 fs0 fc0 sc0 ls4 ws4">the collapse of 32 buildings with 8–12 levels, while more than 150 old buildings with 6–9 levels were</div><div class="t m0 x1 h5 ye ff2 fs0 fc0 sc0 ls3 ws5">seriously damaged. The studies done after this earthquake showed the importance of the surface</div><div class="t m0 x1 h5 yf ff2 fs0 fc0 sc0 ls3 ws6">geological structure upon ground motion parameters. Bonjer<span class="ff1 ls5 ws7"> et al.</span><span class="ls4 ws8"> (1999) used for estimation of the</span></div><div class="t m0 x1 h5 y10 ff2 fs0 fc0 sc0 ls6 ws9">local response the seismic noise recorded at 16 stations in Bucharest. The results showed that the H/V</div><div class="t m0 x1 h5 y11 ff2 fs0 fc0 sc0 ls6 wsa">spectral ratios obtained for the 16 sites are <span class="ls7 wsb">dominated by a clear resonance peak between 1 and 2</span></div><div class="t m0 x1 h5 y12 ff2 fs0 fc0 sc0 ls0 ws0">seconds and their amplitudes remain constant around the value of 2.</div><div class="t m0 x9 h5 y13 ff2 fs0 fc0 sc0 ls4 wsc">Our purpose is to extend the Bonjer<span class="ff1 ls2 wsd"> et al</span><span class="ls8 wse">. (1999) study using new data acquired in 2002 on</span></div><div class="t m0 x1 h5 y14 ff2 fs0 fc0 sc0 ls6 ws9">20 sites in Bucharest. The <span class="_ _3"></span>measurements were done with a K2 digital station equipped with a velocity</div><div class="t m0 x1 h5 y15 ff2 fs0 fc0 sc0 ls6 wsf">sensor having the natural period <span class="_ _3"></span>of 5 seconds. For computation of the spectral ratios using</div><div class="t m0 x1 h5 y16 ff2 fs0 fc0 sc0 ls9 ws10">Nakamura’s method (1989) the JSESAME software developed within the European project SESAME</div><div class="t m0 x1 h5 y17 ff2 fs0 fc0 sc0 lsa ws11">(http://sesame-fp5.obs.ujf-grenoble.fr) was used. The obtained ratios confirm the previous results,</div><div class="t m0 x1 h5 y18 ff2 fs0 fc0 sc0 lsa ws11">showing a dominant resonance in the period range of 1–2 seconds. The average <span class="_ _2"></span>period of these</div><div class="t m0 x1 h6 y19 ff2 fs0 fc0 sc0 ls2 ws12">maxima is 1.47 <span class="_ _4"></span><span class="ff4 ls0 ws0">r<span class="ff2 ls3 ws13"> <span class="_ _4"></span>0.20 <span class="_ _4"></span>s, while the average amplitude is 2.5. Our results bring evidence of the</span></span></div><div class="t m0 x1 h5 y1a ff2 fs0 fc0 sc0 lsb ws14">applicability of the ambient noise measurements and their relevance for the microzonation</div><div class="t m0 x1 h5 y1b ff2 fs0 fc0 sc0 ls0 ws0">assessment studies in the Bucharest area.</div><div class="t m0 x9 h5 y1c ff1 fs0 fc0 sc0 ls0 ws15">Key words:<span class="_ _5"> </span><span class="ff2 ls7 ws16">fundamental period of resonance, seismic microzonation, Nakamura technique,</span></div><div class="t m0 xa h5 y1d ff2 fs0 fc0 sc0 ls0 ws0">site effects.</div><div class="t m0 xb h7 y1e ff5 fs3 fc0 sc0 ls0 ws0">INTRODUCTION</div><div class="t m0 x9 h8 y1f ff2 fs3 fc0 sc0 lsc ws17">The behavior of the ground motion during an earthquake is generally well</div><div class="t m0 x1 h8 y20 ff2 fs3 fc0 sc0 lsd ws18">explained by the geological surface structure in the place where the phenomenon</div><div class="t m0 x1 h8 y21 ff2 fs3 fc0 sc0 lse ws19">is studied<span class="fc1 ls0 ws0">.</span><span class="lsf ws1a"> Past and recent observations have shown that the <span class="_ _2"></span>damage caused by</span></div><div class="t m0 x1 h8 y22 ff2 fs3 fc0 sc0 lsf ws1b">strong earthquakes are more important in sedimentary basins than on hard rock</div><div class="t m0 x1 h8 y23 ff2 fs3 fc0 sc0 lse ws0">structures.</div><div class="t m0 x9 h9 y24 ff3 fs4 fc0 sc0 ls0 ws0"></div><div class="t m0 xc h5 y25 ff2 fs0 fc0 sc0 ls3 ws1c"> Paper presented at the Annual Scientific Conference, May 26, 2006, Faculty <span class="_ _2"></span>of Physics,</div><div class="t m0 x1 h5 y26 ff2 fs0 fc0 sc0 ls0 ws0">Bucharest University, Romania.</div></div><div class="pi" data-data='{"ctm":[1.611639,0.000000,0.000000,1.611639,0.000000,0.000000]}'></div></div> </body> </html>

<div id="pf2" class="pf w0 h0" data-page-no="2"><div class="pc pc2 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/622bb43215da9b288bb860be/bg2.jpg"><div class="t m0 x1 h5 y27 ff2 fs0 fc0 sc0 ls0 ws0">132<span class="_ _6"> </span>Bogdan Zaharia <span class="ff1">et al.<span class="_ _7"> </span></span>2</div><div class="t m0 x9 h8 y28 ff2 fs3 fc0 sc0 ls10 ws1d">The phenomenon responsible for the amplification of the ground <span class="_ _2"></span>motion in</div><div class="t m0 x1 h8 y29 ff2 fs3 fc0 sc0 ls11 ws1e">areas with soft sediments is <span class="_ _3"></span>the trapping of seismic waves within sediments due to</div><div class="t m0 x1 h8 y2a ff2 fs3 fc0 sc0 ls12 ws1f">the acoustic impedance contrast (the product between the mean velocity of the</div><div class="t m0 x1 h8 y2b ff2 fs3 fc0 sc0 ls13 ws20">seismic wave in a layer and its mean density) between sediments and bedrock. The</div><div class="t m0 x1 h8 y2c ff2 fs3 fc0 sc0 ls14 ws21">interference of these “trapped” waves leads to resonances whose shapes and</div><div class="t m0 x1 h8 y2d ff2 fs3 fc0 sc0 ls11 ws22">frequencies are well correlated with the geometrical and mechanical <span class="_ _2"></span>characteristics</div><div class="t m0 x1 h8 y2e ff2 fs3 fc0 sc0 ls0 ws0">of the structure.</div><div class="t m0 x9 h8 y2f ff2 fs3 fc0 sc0 ls15 ws23">The city of Bucharest is <span class="_ _3"></span>situated in the Romanian Plane, at 150–170 <span class="_ _8"></span>km</div><div class="t m0 x1 h8 y30 ff2 fs3 fc0 sc0 ls11 ws24">distance from the Vrancea epicentral zone, area where earthquakes with high</div><div class="t m0 x1 h8 y31 ff2 fs3 fc0 sc0 ls16 ws25">energy (2–3 earthquakes/100 years with M</div><div class="t m0 xd ha y32 ff2 fs2 fc0 sc0 ls0 ws0">w</div><div class="t m0 xe h8 y33 ff2 fs3 fc0 sc0 ls12 ws26"> <span class="_ _9"></span>> <span class="_ _9"></span>7) occur at intermediate-depths</div><div class="t m0 x1 h8 y34 ff2 fs3 fc0 sc0 ls17 ws27">(70–200 km). The geology of the city is characterized by 7 distinct sedimentary</div><div class="t m0 x1 h8 y35 ff2 fs3 fc0 sc0 ls13 ws28">complexes (Fig. 1), with different peculiarities and large intervals of thicknesses.</div><div class="t m0 x1 h8 y36 ff2 fs3 fc0 sc0 ls13 ws29">These shallow Quaternary complexes were first identified and separated by Liteanu</div><div class="t m0 x1 h8 y37 ff2 fs3 fc0 sc0 ls10 ws2a">(1951) and then cited by different authors with minor changes (Lungu<span class="ff1 ls17 ws2b"> et al.</span><span class="ls18 ws2c">, 1999;</span></div><div class="t m0 x1 h8 y38 ff2 fs3 fc0 sc0 ls0 ws0">Ciugudean and Stefanescu, 2005; Hannich <span class="_ _a"></span><span class="ff1">et al.</span>, 2005).</div><div class="t m0 x9 h7 y39 ff2 fs3 fc0 sc0 ls15 ws2d">Layer 1: <span class="ff5 ls19 ws2e">Recent surface sediments</span><span class="ws23">, made up of vegetal soil and clayey</span></div><div class="t m0 x1 h8 y3a ff2 fs3 fc0 sc0 ls0 ws0">sediments, with a thickness locally reaching 15 m.</div><div class="t m0 x9 h7 y3b ff2 fs3 fc0 sc0 ls15 ws2f">Layer 2: <span class="ff5 ls11 ws30">Upper sandy-clayey complex</span><span class="ls1a ws31">, constituted of loess formations,</span></div><div class="t m0 x1 h8 y3c ff2 fs3 fc0 sc0 ls1a ws32">often moisture sensitive, with sand layers and overall thickness of 16 m in the <span class="_ _2"></span>north</div><div class="t m0 x1 h8 y3d ff2 fs3 fc0 sc0 ls0 ws0">and less than 1m on the river side.</div><div class="t m0 x9 h7 y3e ff2 fs3 fc0 sc0 ls15 ws33">Layer 3: <span class="ff5 ls12 ws34">Colentina gravel complex</span><span class="ls16 ws35">, made up of gravel and sand (with large</span></div><div class="t m0 x1 h8 y3f ff2 fs3 fc0 sc0 ls16 ws36">variations in the grain size) and frequently with water bearing, clayey layers, with a</div><div class="t m0 x1 h8 y40 ff2 fs3 fc0 sc0 ls0 ws0">variable phreatic level from 1.5 m to 14.0 m. Thickness locally reaches 20 m.</div><div class="t m0 x9 h7 y41 ff2 fs3 fc0 sc0 ls16 ws37">Layer 4:<span class="ff5 ls14 ws38"> Intermediate clay complex</span><span class="ls10 ws39">, made up of alternating brown and grey</span></div><div class="t m0 x1 h8 y42 ff2 fs3 fc0 sc0 ls15 ws3a">clays, with intercalation of hydrological fine confined sandy layers. The thickness</div><div class="t m0 x1 h8 y43 ff2 fs3 fc0 sc0 ls12 ws3b">of this layer reaches a 23 m maximum in the north of the city, but towards the</div><div class="t m0 x1 h8 y44 ff2 fs3 fc0 sc0 ls0 ws0">south it becomes very thin and disappears.</div><div class="t m0 x9 h7 y45 ff2 fs3 fc0 sc0 ls15 ws3c">Layer 5: <span class="ff5 ls1b ws3d">Mostiºtea sand complex</span><span class="ls1a ws3e">, a confined water-bearing layer made up</span></div><div class="t m0 x1 h8 y46 ff2 fs3 fc0 sc0 ls12 ws3f">of fine grey sands with lenticular intercalation of clay. Its thickness varies from</div><div class="t m0 x1 h8 y47 ff2 fs3 fc0 sc0 ls0 ws0">10 m to 15 m and is continuously extending around Bucharest city.</div><div class="t m0 x9 h7 y48 ff2 fs3 fc0 sc0 ls15 ws40">Layer 6: <span class="ff5 ls1c ws41">Lacustrine complex</span><span class="ws42">, with thickness of 10 m–60 m, made of clays</span></div><div class="t m0 x1 h8 y49 ff2 fs3 fc0 sc0 ls12 ws43">and silty clays, with small lenticular sandy layers, most frequently situated at the</div><div class="t m0 x1 h8 y4a ff2 fs3 fc0 sc0 ls17 ws44">top of this complex. The gray colour and also the limestone content show that the</div><div class="t m0 x1 h8 y4b ff2 fs3 fc0 sc0 ls0 ws0">conditions are typical for a lacustrine facies.</div><div class="t m0 x9 h7 y4c ff2 fs3 fc0 sc0 ls15 ws32">Layer 7: <span class="ff5 ls11 ws45">Frãteºti sands complex,</span><span class="ls13 ws46"> the deepest bearing stratum with a</span></div><div class="t m0 x1 h8 y4d ff2 fs3 fc0 sc0 ls1a ws47">thickness of 100 m to <span class="_ _3"></span>180 m, including A, B, C Frãteºti levels. It is made up of</div><div class="t m0 x1 h8 y4e ff2 fs3 fc0 sc0 ls17 ws44">sands and gravel, from which industrial and drinking water is usually pumped out</div><div class="t m0 x1 h8 y4f ff2 fs3 fc0 sc0 ls0 ws0">(Ciugudean and Stefanescu, 2005).</div><div class="t m0 x9 h8 y50 ff2 fs3 fc0 sc0 ls1c ws0">Bala<span class="ff1 ls17 ws48"> et al.</span><span class="ls15 ws2d"> (2006) determined the dynamic soil parameters by down-hole</span></div><div class="t m0 x1 h8 y51 ff2 fs3 fc0 sc0 ls1b ws49">seismic measurements performed in 10 locations (boreholes) in Bucharest. These</div><div class="t m0 x1 h8 y52 ff2 fs3 fc0 sc0 ls1d ws4a">measurements re<span class="_ _3"></span>pre<span class="_ _3"></span>se<span class="_ _3"></span>nte<span class="_ _3"></span>d a co<span class="_ _3"></span>mb<span class="_ _3"></span>ine<span class="_ _3"></span>d effort of the National Institute for Earth</div></div><div class="pi" data-data='{"ctm":[1.611639,0.000000,0.000000,1.611639,0.000000,0.000000]}'></div></div>

<div id="pf3" class="pf w0 h0" data-page-no="3"><div class="pc pc3 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/622bb43215da9b288bb860be/bg3.jpg"><div class="t m1 xf hb y53 ff2 fs5 fc2 sc0 ls1e ws4b">Fig. 1 – Lithological cross-section for Bucharest area (after Mandrescu<span class="ff1 ws4c"> et al.</span><span class="ls1f ws4d">, 2004). One can notice the dipping of the sediments towards north.</span></div></div><div class="pi" data-data='{"ctm":[1.611639,0.000000,0.000000,1.611639,0.000000,0.000000]}'></div></div>