css如何实现水纹扩散的动画效果（纯代码）

<div class="main clearfix">
 <!--3*70=210 2*50=100 310-->
 <div class="circle">
 <!--<div class="box"></div>-->
 <div class="box-a"></div>
 <div class="box-b"></div>
 <div class="box-c"></div>
 <div class="box-icon icon-a icon-a-1"></div>
 </div>
 <!--hr正常灰色 hr-x出错 hr-r正确-->
 <div class="hr hr-x"></div>

 <div class="circle">
 <!--<div class="box"></div>-->
 <div class="box-a"></div>
 <div class="box-b"></div>
 <div class="box-c"></div>
 <div class="box-icon icon-b icon-b-2"></div>

 </div>
 <div class="hr hr-r"></div>

 <div class="circle">
 <!--<div class="box"></div>-->
 <div class="box-a"></div>
 <div class="box-b"></div>
 <div class="box-c"></div>
 <div class="box-icon icon-c icon-c-3"></div>
 </div>
</div>

.main{
 position: relative;
 height:70px;
 width: 310px;
 margin: 0 auto;
 background-color: #f34147;
}
.circle{
 position: relative;
 float: left;
 height:70px;
 width: 70px;


}
/*线*/
.hr{
 position: relative;
 float: left;
 width: 50px;
 height:70px;
 background: url("../images/hr_1.png") no-repeat center center;
 background-size: auto 18px;

}
.hr-x{
 background: url("../images/hr_2.png") no-repeat center center;
 background-size: auto 18px;
}
.hr-r{
 background: url("../images/hr_3.png") no-repeat center center;
 background-size: auto 18px;
}

/*按钮 大：47 小：39*/
.box-icon{
 position: absolute;
 z-index: 9999;
 top:0;
 right:0;
 left:0;;
 bottom: 0;
 width: 70px;
 height: 70px;
}
/*小 不亮*/
.icon-a{
 background: url("../images/icon_a_3.png") no-repeat center center;
 background-size:39px 39px;
}
.icon-b{
 background: url("../images/icon_b_3.png") no-repeat center center;
 background-size:39px 39px;
}
.icon-c{
 background: url("../images/icon_c_3.png") no-repeat center center;
 background-size:39px 39px;
}
/*小 亮*/
.icon-a-1{
 background: url("../images/icon_a_2.png") no-repeat center center;
 background-size:39px 39px;
}
.icon-b-1{
 background: url("../images/icon_b_2.png") no-repeat center center;
 background-size:39px 39px;
}
.icon-c-1{
 background: url("../images/icon_c_2.png") no-repeat center center;
 background-size:39px 39px;
}


/*大 亮*/
.icon-a-2{
 background: url("../images/icon_a_1.png") no-repeat center center;
 background-size:47px 47px;
}
.icon-b-2{
 background: url("../images/icon_b_1.png") no-repeat center center;
 background-size:47px 47px;
}
.icon-c-2{
 background: url("../images/icon_c_1.png") no-repeat center center;
 background-size:47px 47px;
}


/*动效*/
@keyframes warn {
 0% {
 transform: scale(0.6);
 opacity: 0;
 }
 25% {
 transform: scale(0.6);
 opacity: 0.8;
 }
 /*50% {*/
 /*transform: scale(0.8);*/
 /*opacity: 0.4;*/
 /*}*/
 /*75% {*/
 /*transform: scale(0.9);*/
 /*opacity: 0.3;*/
 /*}*/
 100% {
 transform: scale(1);
 opacity: 0.1;
 }
}
@-webkit-keyframes warn {
 0% {
 -webkit-transform: scale(0);
 opacity: 0;
 }
 25% {
 -webkit-transform: scale(0.6);
 opacity: 0.8;
 }
 /*50% {*/
 /*-webkit-transform: scale(0.1);*/
 /*opacity: 0.3;*/
 /*}*/
 /*75% {*/
 /*-webkit-transform: scale(0.5);*/
 /*opacity: 0.5;*/
 /*}*/
 100% {
 -webkit-transform: scale(1);
 opacity: 0.1;
 }
}
/* 70*70的容器*/
.box{
 position: absolute;
 width: 70px;
 height: 70px;
 border: 6px solid rgba(225,225,225,0.5);
 -webkit-border-radius:70px;
 -moz-border-radius: 70px;
 border-radius: 70px;
 z-index: 1;
 opacity: 0;
 -webkit-animation: warn 4s ease-out infinite;
 -moz-animation: warn 4s ease-out infinite;
 animation: warn 4s ease-out infinite;
}
.box-a{
 position: absolute;
 width: 70px;
 height: 70px;
 border: 6px solid rgba(225,225,225,0.5);
 -webkit-border-radius:70px;
 -moz-border-radius: 70px;
 border-radius: 70px;
 z-index: 1;
 opacity: 0;
 -webkit-animation: warn 4s ease-out infinite;
 -moz-animation: warn 4s ease-out infinite;
 animation: warn 4s ease-out infinite;
 animation-delay:1s;
 -webkit-animation-delay:1s; /* Safari 和 Chrome */


}
.box-b{
 position: absolute;
 width: 70px;
 height: 70px;
 border: 6px solid rgba(225,225,225,0.5);
 -webkit-border-radius:70px;
 -moz-border-radius: 70px;
 border-radius: 70px;
 z-index: 1;
 opacity: 0;
 -webkit-animation: warn 4s ease-out infinite;
 -moz-animation: warn 4s ease-out infinite;
 animation: warn 4s ease-out infinite;
 animation-delay:2s;
 -webkit-animation-delay:2s; /* Safari 和 Chrome */

}
.box-c{
 position: absolute;
 width: 70px;
 height: 70px;
 border: 6px solid rgba(225,225,225,0.5);
 -webkit-border-radius:70px;
 -moz-border-radius: 70px;
 border-radius: 70px;
 z-index: 1;
 opacity: 0;
 -webkit-animation: warn 4s ease-out infinite;
 -moz-animation: warn 4s ease-out infinite;
 animation: warn 4s ease-out infinite;
 animation-delay:3s;
 -webkit-animation-delay:3s; /* Safari 和 Chrome */
 
}