定位震中位置

Can you find an earthquake epicenter?
::你能找到地震中心吗?

The  epicenter  of the 2011 Japan   was just offshore of Sendai. This is where the Pacific  Plate  plunges into a  subduction zone . The earthquake had a relatively shallow depth of 20 miles (32 km). Remember that shallow quakes typically cause the most damage. How do scientists find an earthquake epicenter?
::2011年日本的震中在仙台的岸外。 这是太平洋板块跳入潜入潜入区的地方。 地震的深度相对浅,为20英里( 32公里 ) 。 记住浅地震通常造成最大的破坏。 科学家如何发现地震震中?

Finding the Epicenter
::寻找 Epicent

One  seismogram  indicates the distance to the epicenter. This is determined by the P-and  S-wave  arrival times. If a quake is near the  seismograph , the  S-waves  arrive shortly after the P-waves. If a quake is far from the seismograph, the P-waves arrive long before the S-waves. The longer the time is between the P-and S-wave arrivals, the further away the earthquake was from the seismograph. First, seismologists calculate the arrival time difference. Then they know the distance to the epicenter from that seismograph. They can connect all the points that are that distance from the seismic station. This makes a circle around the station!
::一台地震图显示震中距离。 这由P- S波到达时间决定。 如果地震接近地震仪, S波就会在P波过后不久到达。 如果地震离地震仪很远, P波就会在S波之前很久到达。 P- S波到达的时间越长,地震距离地震仪越远。 首先, 地震学家计算到达时间差。 然后他们知道地震仪离震波中心有多远。 他们可以连接地震台距离的所有点。 这在地震台周围环绕一个圆圈 !

Next, the seismologists try to determine the   of the earthquake epicenter. To do this they need the distances to the epicenter from at least three seismographs. Let’s say that they know that an earthquake’s epicenter is 50 kilometers from Kansas City. They draw a circle with a 50 km radius around that seismic station. They do this twice more around two different seismic stations. The three circles intersect at a single point. This is the earthquake’s epicenter ( Figure   ).
::接下来,地震学家试图确定地震震中心。 要做到这一点,他们需要至少从三个地震摄影师到震中心之间的距离。让我们假设他们知道地震震中心离堪萨斯市有50公里。他们在地震台站周围画了一个半径50公里的圆圈。他们在两个不同的地震台站周围画了两倍的圆圈。三个圆圈在一个点交叉。这是地震的震中(图示 ) 。

Summary
::摘要

• To find an earthquake epicenter you need at least three seismographs.
  ::要找到地震中心,你至少需要三个地震仪。

• Find the distance from each seismograph to the earthquake epicenter.
  ::找到从每个地震摄像到地震中心之间的距离。

• The interception of the three circles is the epicenter.
  ::三个圈子的拦截是震中

Review
::回顾

1. How do you determine the distance from the seismograph to the earthquake epicenter?
   ::你如何确定从地震摄像到地震中心之间的距离?

1. How do you find the epicenter from three seismographs?
   ::你如何从三个地震仪中找到震中?

1. What role does the S-P interval play in locating an earthquake epicenter?
   ::S-P间隔在确定地震震中的位置方面起什么作用?