【正文】 the building was inadequate and most of the bolts failed. Building deflections following failure of the bracing caused an interior column to punch through a floor slab. Extensive damage to shear walls above door openings also occurred. Tiltup Buildings 28 Concrete tiltup buildings are the most mon form of modern lowrise industrial and mercial construction throughout California. They usually are constructed with plywood sheathed woodframe roofs supported by perimeter concrete walls. They are called tiltups because the perimeter walls are constructed lying flat against the floor slab and then tiltedup into position around the building. Extensive damage to these buildings has been observed in past earthquakes, including the 1987 Whittier and 1971 San Fernando events. Thousands of tiltup buildings are present in the affected region. Although some significant damage was experienced near the epicenter, the greatest concentrations of these buildings are located in areas that experienced very weak ground motion. Most of these buildings therefore had little damage. Several buildings in Hollister were investigated. Several tiltup building partially collapsed as the result of inventories of stacked cans containing tomato product impacting the walls during the earthquake. Damage was extensive. Much of the inventory was lost or severely damaged. This underscores the importance of addressing seismic issues relating to equipment and contents, as well as structural designThe buildings appeared to be late 1960s or early 1970s vintage and as such were observed not to have rooftowall anchors. These anchors were required following collapses of tiltups during the San Fernando Earthquake in 1971. Much of the roof of a half of one building occupied by the adjacent tenant also collapsed, causing extensive interior damage In Watsonville, several panels of a large tiltup owned by a food packager bowed outward at midheight and approached collapse. Concrete spalled off of several of the pilasters in the building wall, exposing the reinforcing steel, some of which buckled. In another, newly constructed Watsonville tiltup, interpanel connections at a skewed corner were damaged and roof sheathing was severely torn. Steel Buildings Modern steelframe buildings performed excellently in this earthquake, as they have in the past. Damage to these structures was typically limited to cracking of cladding and interior partitions and widespread disarray of contents. The nonstructural damage 29 sustained by steelframe buildings may largely be attributed to their flexibility, which results in very large displacements. A steelframe building with corrugated metal siding in Hollister serves as a warehouse for a food pany. As with the concrete tiltup buildings in Hollister, this tomato packing pany experienced severe damage to its steelframe building and significant loss of inventory. Canned tomato products stacked over 30 feet high on standard pallets were mobilized by the earthquake. Most stacks collapsed, impacting and ripping through the corrugated metal side walls. Impact forces were so great that several tapered steel columns and beams were severely damaged. These steel members twisted, bent, and failed, taking down an entire section of the building. Much of the inventory was lost or severely damaged. As with concrete tiltup warehouses, this incident highlights the effect that stored inventory can have on the integrity of a building during an earthquake. Summary The remote epicentral location of this earthquake allowed the San Francisco Bay Area to survive with relatively few instances of structural collapse. Except for buildings near the epicenter, most cases of severe damage occurred in older buildings with little seismic capacity and in areas of extremely weak soils. The fact that many inadequate structures in the region experienced little damage indicates that ground motion in most areas was not severe. Even so, most businesses experienced at least a week39。 這個(gè) San Andreas Fault 30 英里長(zhǎng)的裂縫并沒(méi)有改變?cè)谖磥?lái) 30 年里再次發(fā)生一個(gè)或者幾個(gè) 級(jí)地震的可能性，這個(gè)可能性是 50％。在 Highway 17 二條小路被一個(gè)在山頂西部發(fā)生的巨大的滑坡堵死。 地震導(dǎo)致了成百上千的沿著陡峭斜坡的滑坡，從震中 地區(qū)的山上到至少遠(yuǎn)至在 San Francisco 南部的太平洋彼岸。在 San Francisco，先前的液化破壞發(fā)生在 Ft. Mason 附近，與在 Marina 區(qū)域的當(dāng)前的破壞的位置相近，還有就是沿著 waterfront 的商業(yè)區(qū)，在那里 Embarcadero 高速公路和許許多多的古老的磚石建筑都受到了破壞。 與在 San Francisco 和 Oakland 的與液化和土壤因素有關(guān)的的破壞的類型與1906 年的相似。液化影響在受到最嚴(yán)重破壞的區(qū)域 San Francisco 的 Marina 地區(qū)被廣泛注意。在這些遙遠(yuǎn)地區(qū)的更為強(qiáng)烈的地殼運(yùn)動(dòng)反映了土壤震動(dòng)密度的影響。相對(duì)低的加速度在震中和 Oakland 以及 San Francisco 之間的地方 被記錄到。 地殼運(yùn)動(dòng)紀(jì)錄 我們從數(shù)百個(gè)儀器中得到強(qiáng)烈的運(yùn)動(dòng)紀(jì)錄，允許通過(guò)一整個(gè)受到影響的地區(qū)的細(xì)節(jié)理解。過(guò)去的地震的發(fā)生是由于兩邊斷層的水平位移，西南端向西北端相對(duì)東北端運(yùn)動(dòng)。 在 Santa Cruz 地區(qū)的最近的一次破壞性強(qiáng)的地震包括一個(gè) 1964 年 11 月 15日發(fā)生的 級(jí)地震， 導(dǎo)致了煙囪的破壞；還有 1988 年 6 月發(fā)生的 級(jí)地震和 24 這一年 8 月發(fā)生的 級(jí)地震，都和 Loma Prieta 地震發(fā)生在幾乎相同的區(qū)域。 fault 的破裂長(zhǎng)度通常是從 1906 年破裂的楠端伸展，因此從那時(shí)起，就有山脈開(kāi)始聚集形成。它是許多大地震的源頭，包括 1865 年 Santa Cruz 東北部的地震，以及著名的 1906 年 級(jí) San Francisco地震。國(guó)家委員會(huì) 1906年地震的報(bào)告描述了沿著 San Andreas Fault 的 Santa Cruz 山的非常相似的地表破裂特征。地震相當(dāng)深，使得巖床破裂至地表變得困難。但 是我們?cè)诓婚g斷的模糊區(qū)域發(fā)現(xiàn)許多的裂縫。在深度上，區(qū)域從 2 至 11 英里延伸，我們有理由相信，破裂的長(zhǎng)度是和主震相聯(lián)系的。余震區(qū)從接近 Highway 17 的 Los Gatos 北部延伸到 接近 Highway 101 的 Watsonville 南部 ，跨越了 25 英里。在地震以后的那個(gè)星期里，有大約 300 個(gè)余震達(dá)到 級(jí)，還有大約 20 個(gè)達(dá)到 4。 一個(gè) 級(jí) 的余震在主震之后發(fā)生了，持續(xù)了大約 2。震深達(dá)到了 11 英里。土壤的劣質(zhì)不是導(dǎo)致建筑物倒塌的直接原因，然而它們毫無(wú)疑問(wèn)的對(duì)整個(gè)事件產(chǎn)生了影響。這些角落上的建筑也會(huì)彎曲，進(jìn)一步使得它們的性能惡化。第二，幾乎所有的倒塌和幾乎倒塌的建筑物有相同的配置：這些建筑的第一層都有很多停車場(chǎng)的入口，缺乏切變強(qiáng)度或者稱為軟層。 這些建筑物被破壞的主要原因有兩個(gè)。盡管在 Marina 街區(qū)的所有的建筑物中都可以發(fā)現(xiàn)石膏和灰泥的破裂，最嚴(yán)重的破壞發(fā)生在中層（ 4 至 5 層）。這些建筑大多數(shù)在第一層都有停車場(chǎng)。這個(gè)街區(qū)的土壤主要是由松軟的，滲透性的泥沙組成，其中一些是自然形成的，但是大多數(shù)都是在大約 1915 年的巴拿馬－太平洋博覽會(huì)時(shí)填充進(jìn)去的。它的內(nèi)部也沒(méi)有損壞，甚至夾板都沒(méi)有破裂。在 Watsonville 的一個(gè)街區(qū)，只有一個(gè)房子沒(méi)有從它的地基上脫落。顯然，一些經(jīng)過(guò)結(jié)構(gòu)性修復(fù)的老房子可以有結(jié)構(gòu)上的升級(jí)。在有一個(gè)街區(qū)，五分之一的住所的跛墻都被破壞。在南太平洋公園街的太平洋街，幾乎所有的住宅樓都被破壞了。在Watsonville，在整個(gè)地區(qū)，大約有 10％至 20％的 40 年代以前的住宅樓的跛墻被損壞，許多街區(qū) 100％的住宅樓都被損壞。這些建筑從幾個(gè)英寸向一個(gè)英尺側(cè)移，直到跛墻變得不穩(wěn)固和倒塌。由于它們沒(méi)有覆蓋石膏，正如生活區(qū)的墻壁一樣，它們非常脆弱，是一個(gè)經(jīng)常破損的區(qū)域。 對(duì)住宅樓的嚴(yán)重結(jié)構(gòu)性損壞可以歸結(jié)為跛墻的不牢固，以及基石