When the instrument is situated at more than 700 miles from the earthquake centre, the graphic record shows three waves arriving one after the other at short intervals.

one after the other = one after another ^{used to talk about a series of similar things or events 一个接一个地}

• I'll eat chocolates one after the other until the box is finished.
• Small businesses have been collapsing one after another.

interval ^{n. （时间上的）间隔；（空间上的）间距}

• at weekly / 20 minute intervals
• The trains run at hourly intervals.
• The trees were planted at 20 meter intervals.
• But suppose the earth could be covered with sensors spaced one foot apart, rising at one-foot intervals all the way to the top of the atmosphere.
• Indeed, it may well be that those whose work is their pleasure are those who most need the means of banishing it at intervals from their minds.
• There was a short interval of peace before the noise started again. ^{在噪音再次开始前，有一段短暂的宁静。}
• The security camera took pictures at short intervals throughout the night.^{这台安全摄像机整晚都以短间隔拍照。}

The first records the arrival of longitudinal vibrations.

records the arrival of ^{记录…的到达}

• The first records the arrival of longitudinal vibrations.^{第一个记录了纵向振动的到达。}
• The sensor records the arrival of the first seismic activity.^{传感器记录了首次地震活动的到达。}

longitudinal vibrations ^纵向振动

• The results show that longitudinal vibration of drill string is relative to rotary speed and weight on bit (WOB). ^{实验结果表明，钻柱的纵向振动主要与转速和钻压有关。}
• The expression format and application method of longitudinal vibration road spectrum were described. ^{建立了纵振动力学模型，阐述了纵振路面谱的表达形式及应用方法。}
• In this paper, the regularity of longitudinal vibration was analyzed by using finite element method. ^{本文利用有限元方法分析了钻柱轴向振动规律。}

The second marks the arrival of transverse vibrations which travel more slowly and arrive several minutes after the first.

mark the arrival of ^{标志着…的到达}

• The loud whistle marks the arrival of the express train.^{响亮的汽笛声标志着特快列车的到达。}
• The snow signalled the arrival of a front, and a high-pressure area seemed to be settling in. ^{降雪标志了一个锋面的到来，一个高压区似乎正在进入本地。}
• With the arrival of spring, the refugees will be moved again. ^{随着春天的到来，难民们将再次被转移。}

These two have travelled through the earth.

through the earth ^{贯穿地球（传播）}

• I want to dig a hole all the way through the earth! ^{我想挖一个贯穿地球的洞。}
• I wonder if I shall fall right through the earth! ^{我想知道我会不会正好穿过地球掉下去！}
• The deep-sea currents have travelled through the ocean basins for millennia.^{深海洋流穿过洋盆传播了数千年。}

It was from the study of these that so much was learnt about the interior of the earth.

interior ^{n. the inner part or inside of something 内部，里面}

• The interior of the church was dark.
• a house with a classical exterior and a modern interior

The third, or main wave, is the slowest and has travelled round the earth through the surface rocks.

or ^{conj. (introducing a word or phrase that explains, or means the same as, another 表示一词语对另一词语的解释关系或为其同义词语) 即，亦即，或者说}

• a kilo, or two pounds
• geology, or the science of the earth's crust
• Cave exploration, or pot-holing, as it has come to be known, is a relatively new sport.